question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p><img src="http://i.stack.imgur.com/DXzxU.png" alt="enter image description here"></p>
<p>I have absolutely no knowledge of statistics. My question is how to make sense of some evaluation results I received. The attached graph represents my results of a Likert question compared to my department, division, and colleg... | g15068 | [
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<p>I am planning my wedding. I wish to estimate how many people will come to my wedding. I have created a list of people and the chance that they will attend in percentage. For example</p>
<p><code>Dad 100%
Mom 100%
Bob 50%
Marc 10%
Jacob 25%
Joseph 30%</code></p>
<p>I have a list of about 230 people with pe... | g58058 | [
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<p>I have weekly data for the last four years. I am using SPSS to do forecasting. I am getting a constant value in the forecast period. What could be the reason behind it? Is it due to defining weekly dates? I am not able to figure it out.</p>
<p>I have defined the week dates using following code:</p>
<p><code>DATE W... | g58059 | [
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<p>In Machine Learning, there are various models. I tried to learn few probabilistic models of Machine Learning. I read the theory, worked on problems and tested my results and could analyze my data according to the need like classification, etc.</p>
<p>I am a Computational Linguist and I am trying to post many questi... | g36829 | [
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<p>If I have a problem down to </p>
<p>$$k(E(x^2) - E(x)^2) = E(\overline{x}^2) - E(\overline{x})^2$$</p>
<p>...can I say $k = 1$? $X$ has an unbiased mean and a variance. Each $x$ in $X$ is independent.</p>
<p>Or is it more complex than that? If it's not clear, $\overline{x}$ signifies the average (or mean or wha... | g12940 | [
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<p>Assume 3 random variables, $A, B, C$.</p>
<p>If $A \perp B$, but $Cov(B,C) \neq 0$, can we say anything about $Cov(A,C)$? I think it can either be 0 or not 0, but it seems like there should be more general results than that. </p> | g58060 | [
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<p>I pose a very similar question to <a href="http://stats.stackexchange.com/questions/26531/do-zero-inflated-continuous-covariates-cause-problems-in-binary-logistic-regre/">this</a>, although I felt the advice given does not apply to my particular situation;</p>
<p>I am using logistic regression models for an animal ... | g58061 | [
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<p>I am arguing that I can control error vs. coverage by modifying a certain parameter. After running an experiment with leave-many-out validation I have a set of errors along with the parameter value for each error. I want to visualize how I can trade coverage for accuracy by placing restrictions on my parameter.</p>
... | g58062 | [
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<p>Background: I am an evolutionary biologist interested in how morphological variation within a population of individuals contributes to variation in their competitive ability. To get at this in the tadpoles that I work on, I want to create a 'morphological index' that incorporates four different traits that are thou... | g2987 | [
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<p>I am trying to find out the best method for determining the source of a significant MANCOVA interaction. I have 17 traits measured for four locations. Is there an alternate to univariate ANCOVAs investigating each trait independently? These are body measurements which aren't independent of one another, so it would b... | g58063 | [
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<p>I got there example graphs bishop's PRML (8.2.1)<br>
1. <strong>a <- c -> b</strong><br>
$$
p(a,b,c) = p(a|c)p(b|c)p(c) --(1)\\
p(a,b) = \sum_c p(a|c)p(b|c)p(c) --(2)
$$
<strong>Q1</strong>: Can I use a new graph to represent the p(a,b) in formula (2) ?</p>
<p>2.<strong>a->c->b</strong>
$$
p(a,b,c) = p(a)... | g58064 | [
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<p>I am working with a highly class-skewed three class classification problem. The class percentages are A = 1.8%, B = 17.5% and C = 80.7%. According to <a href="https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDcQFjAB&url=http://www.hpl.hp.com/techreports/... | g58065 | [
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<p>I am implementing a C4.5 algorithm, and for that I need to perform attribute selection. How do I use the gain and split info equation to find the best attribute?</p> | g49521 | [
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<p>My data is $(Y,X)_i,i=1...N$ and i want to fit a regression model to relate $Y$ and $X$.</p>
<p>It is known that $X$ and $Y$ are erroneous measurement of true variable $(U,V)$, but the standard errors $(\sigma_X,\sigma_Y)_i, i=1...N$ are known to me. I also know that the standard error is correlated with the true v... | g12951 | [
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<p>I have been using <code>lmp</code> function from <a href="http://cran.r-project.org/web/packages/lmPerm/index.html" rel="nofollow">lmPerm</a> package to calculate differences between treatment levels (2-ANOVA). Now, I am wondering how to report <code>lmp</code> results in a scientific publication?</p>
<p>I am aimin... | g58066 | [
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<p>I have two sets of experimental data for exponential decays of isotopes and I calculated the ratio of the two isotopes as a function of time. The theoretical model and the fit of the experimental data are respectively :</p>
<p>$1.04\text{e}^{-0.000856008t}$</p>
<p>$1.03154\text{e}^{-0.000457549t}$</p>
<p>The two ... | g12954 | [
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<p>Suppose we have a mixed model for repeated measures with response being $y$ and a covariate being $x$(say, age). There are two classification factors $a$ and $b$. Say, 5 psychological patients($a$) in 8 conditions($b$) are measured. </p>
<p>I want to know how I get the estimates of intercepts and slopes (and their ... | g58067 | [
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<p>I am using SVM for classification and I am trying to determine the optimal parameters for linear and RBF kernels. For the linear kernel I use cross-validated parameter selection to determine C and for the RBF kernel I use grid search to determine C and gamma.</p>
<p>I have 20 (numeric) features and 70 training exam... | g58068 | [
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<p>Consider collaborative filtering problem. We have matrix $M$ of size #users * #items. $M_{i,j} = 1$ if user i likes item j, $M_{i,j} = 0$ if user i dislikes item j and $M_{i,j}=?$ if there is no data about (i,j) pair. We want to predict $M_{i,j}$ for future user, item pairs.</p>
<p>Standard collaborative filtering ... | g12956 | [
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<p>I am trying to understand the big picture of statistical tests. That is how to choose the correct statistical test under different situations. I found <a href="http://bama.ua.edu/~jleeper/627/choosestat.html" rel="nofollow">this table</a> where choosing a statistical test is based on the types of the dependent and i... | g58069 | [
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<p>I do canonical correlation analysis between two multivariate datasets $X$ and $Y$. For each pair of canonical variates (x-y pair) I get the canonical correlation coefficient. How can I test its statistical significance?</p> | g58070 | [
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<p><img src="http://i.stack.imgur.com/tb2va.png" alt="enter image description here"></p>
<p>I was reading this paper related to <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.110.4050&rep=rep1&type=pdf" rel="nofollow">topic models</a>. I am a bit confused why the marginal likelihood is not t... | g58071 | [
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<p>In a random sample of 150 community college students, the mean number of hours spent studying per week is 11.7 hours and the standard deviation is 4 hours.</p>
<p>Without assuming anything about the distribution of the number of hours community college students study per week, at least what percentage (approximatel... | g12960 | [
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<p>I have a symbolic representation of time series obtained from <a href="http://www.cs.ucr.edu/~eamonn/SAX.htm" rel="nofollow">SAX toolbox</a>. I was wondering if it is possible to construct a graph where each node represents a unique symbol and the edges represent the transition providing that there is no transition ... | g58072 | [
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<p>I'm intending to implement the following factorial design</p>
<p>I wish to obtain this alias structure - with a 2^(5-2) factorial design. </p>
<pre><code>I+ACE+BDE+ABCD
A+CE+ABDE+BCD
B+ABCE+DE+ACD
C+AE+BCDE+ABD
D+ACDE+BE+ABC
E+AC+BD+ABCDE
AB+BCE+ADE+CD
AD+CDE+ABE+BC
</code></pre>
<p>I've obtained this (the alias ... | g58073 | [
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<p>Suppose a business is operating at the three-sigma quality level. If projects have an average improvement rate of 50% annually, how many years will it take to achieve six-sigma quality?</p> | g15075 | [
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<p>I have a question concerning the interpretation of the final cluster centers. I performed a cluster analysis based on a pca (the variables are based on a five point Likert-scale). I got the following result for one factor:</p>
<pre><code> cluster_1 cluster_2 cluster_3 cluster_4 cluste... | g58074 | [
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<p>I am attempting to carry out a discrete time survival analysis using a logistic regression model, and I'm not sure I completely understand the process. I would greatly appreciate assistance with a few basic questions.</p>
<p>Here is the set up:</p>
<p>I'm looking at membership in a group within a five year time w... | g43600 | [
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<p>I am using the GBM package to create a prediction model. Can GBM handle categorical predictors, or do I need to create a model matrix before I input ?</p> | g37441 | [
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<p>I am trying to create a linear regression model. I split my data into training and testing data, and built a model. The R-squared value on the training data is 0.840. Then I ran the model on the test data. When I calculate R-squared, I get 0.982:</p>
<pre><code>y.predicted <- predict(lm1, newdata=test)
y.act... | g58075 | [
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0.04895051196217537,
-0.... |
<p>If the odds ratio is greater than one with an insignificant p value for a variable in logistic regression should the variable be kept in the model?</p>
<p>Can I select the variable with odds close to 1?</p>
<p>Question 2: In the validation and testing dataset do not have same mean how to handle it?</p> | g21312 | [
-0.0007418618188239634,
-0.041449014097452164,
0.017269056290388107,
-0.01665487140417099,
0.017137812450528145,
0.012213537469506264,
-0.019882546737790108,
0.022382348775863647,
-0.055683135986328125,
-0.014484254643321037,
0.014212487265467644,
0.04598570987582207,
-0.010066583752632141,
... |
<p>I'm having trouble regarding which test to run on my data in SPSS.</p>
<p>I have two groups (condition1 and condition2) which is also my independent variable (categorical).</p>
<p>Both groups were asked to rate their brand attitude (dependent variable 1) and purchase intention (dependent variable 2) at two points ... | g58076 | [
-0.038341861218214035,
-0.04546697065234184,
-0.012969929724931717,
-0.016546523198485374,
-0.0271589457988739,
-0.021774739027023315,
-0.015101190656423569,
0.03211018070578575,
0.007937798276543617,
-0.01962355151772499,
0.0478285513818264,
0.05524628981947899,
-0.016840163618326187,
0.0... |
<p>I want to fit an ARIMA model to my data, however I don't know how to select the best ARIMA model using the <code>proc ARIMA</code> command. First of all I know I want to transform my data with the cubic root transformation. </p>
<pre><code>data robberies_cubic_root;
set robberies;
robberiescubicroot=robberies**(1/3... | g58077 | [
0.042163919657468796,
-0.012219407595694065,
-0.0015273826429620385,
-0.013817566446959972,
0.06560396403074265,
-0.022446919232606888,
0.048085395246744156,
-0.0028694586362689734,
-0.05052613094449043,
-0.009001980535686016,
-0.002973944181576371,
0.013353901915252209,
0.040013860911130905... |
<p>I'm looking for a reference for the Naive bayse classifier to put in my work. Not sure what I'm missing but a <a href="http://scholar.google.com/scholar?hl=en&q=Naive%20Bayes%20classifier&btnG=Search&as_sdt=0,5&as_ylo=&as_yhi=&as_vis=1" rel="nofollow">scholar search</a> didn't yield any mean... | g37911 | [
0.009247759357094765,
-0.06580419838428497,
0.012076124548912048,
-0.06563310325145721,
-0.02521541155874729,
0.013532214798033237,
-0.03116515837609768,
0.013185746967792511,
-0.013551783747971058,
-0.023476190865039825,
0.04485161229968071,
0.005953787360340357,
0.08100048452615738,
0.04... |
<p>I have problem in understanding max-min in optimization. I know what does it mean to maximize obejctive function or minimize it, I don't really understand what does it mean to have objective function like max min at the same time. I put example below: </p>
<p><img src="http://i.stack.imgur.com/kFL9C.png" alt="ent... | g58078 | [
-0.008024402894079685,
0.0195175614207983,
0.018546437844634056,
0.03987659886479378,
0.012271758168935776,
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-0.028838487342000008,
0.0030936275143176317,
-0.021623946726322174,
-0.008378802798688412,
-0.07968797534704208,
-0.017426228150725365,
0.047041475772857666,
... |
<p>I am working on a logistic regression approach to predict the clinical status of patients (No disease vs Disease). I already have quite strong evidence indicating that the number of genes hit by a certain kind of variation is significant in predicting disease. Among the genes that I am considering, one of them (gene... | g58079 | [
-0.009027142077684402,
-0.014509634114801884,
0.005152543541043997,
0.014273365028202534,
0.00783357210457325,
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0.005611663684248924,
0.07610733807086945,
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-0.01259560976177454,
-0.0055737802758812904,
0.04785938933491707,
0.030798163264989853,
0.0... |
<p>I was reading this <a href="http://www.phil.frb.org/research-and-data/publications/working-papers/2009/wp09-13.pdf" rel="nofollow">paper</a>. Authors talk about "weakly identified parameters" or "strongly identified parameters" continuously. Rigorously, what does it mean when one say a parameter is strongly or weakl... | g58080 | [
0.06817656010389328,
-0.07023708522319794,
-0.02938428521156311,
0.0006529397796839476,
0.036807235330343246,
-0.007471713237464428,
-0.00950638111680746,
0.05382991582155228,
-0.02524561807513237,
0.021662071347236633,
-0.08676844835281372,
-0.004357823170721531,
0.016035638749599457,
0.0... |
<p>Suppose we have a table of finishing times for an number of 100 metre races where each competition has a different mix of entrants. We suspect that some races are slower than others due to, say, a headwind, but this wasn't measured. How do I find the underlying time for each runner and the correction for each race?<... | g15081 | [
0.03175878897309303,
-0.014693639241158962,
-0.00960460677742958,
-0.04695820435881615,
0.025035450235009193,
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0.11560782790184021,
0.03130539879202843,
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0.0637805312871933,
-0.01494355034083128,
0.009683162905275822,
0.04460063949227333,
0.03772872... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/25671/comparing-smoke-and-hormones-level-in-two-groups-of-people-which-test">Comparing smoke and hormones level in two groups of people. Which test?</a> </p>
</blockquote>
<p>I'm analyzing some data for an... | g49522 | [
-0.02797587215900421,
-0.02173723094165325,
-0.019579492509365082,
-0.028503550216555595,
0.00034010177478194237,
-0.0463419146835804,
0.006532727740705013,
0.03476039692759514,
-0.03443474695086479,
-0.010138609446585178,
0.02709747850894928,
-0.028542054817080498,
0.013474705629050732,
-... |
<p>I got a paper rejected at a conference with the following comment:</p>
<blockquote>
<p>The used method for the analysis is correct, but I find it strange that
the authors evaluate the results as a 4-condition experiment instead of
the 2x2 experiment they set up. This makes their analysis of the
intera... | g12982 | [
0.008068873547017574,
0.01835397258400917,
0.018321923911571503,
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-0.034854236990213394,
0.01923741027712822,
0.01823405735194683,
0.04544210433959961,
0.0287... |
<p>Suppose you have two biased sampling algorithms, and you don't know the bias of the algorithms. Can you combine the algorithms somehow and reduce the bias? </p>
<p>Partly my motivation is discretizing stochastic differential equations. Say you sample using Euler's method and the Milstein method. Both are biased, bu... | g12985 | [
0.006012845318764448,
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0.0325467623770237,
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0.021280642598867416,
0.04394501820206642,
0.050275545567274094,
0.0822625383734703,
0.0557641... |
<p>I've been dealing with the problem of how to construct confidence intervals on penalized spline estimators in the presence of cluster-wise auto-correlation and heteroskedasticity. My previous thread on this is here: <a href="http://stats.stackexchange.com/questions/44798/penalized-spline-confidence-intervals-based-... | g58081 | [
0.021094847470521927,
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-0.006925133056938648,
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0.... |
<p>I have 30 attribute variables with response on a 1 to 5 scale (e.g., extremely important, very important, important, not that important, etc.). I ran factor analysis in SPSS and extracted 6 factors and saved the values using the regression approach. Now I want to understand them. I can make sense of the 6 factors th... | g12986 | [
0.014357992447912693,
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-0.028354963287711143,
0.007692452520132065,
0.016269808635115623,
0.05915217846632004,
... |
<ol>
<li><p>Can a LASSO be applied for predictor selection in a logistic GEE (generalized estimating equations) model for longitudinal data?</p></li>
<li><p>Is there an implementation of LASSO for a logistic GEE model for longitudinal data in either R or MATLAB?</p></li>
</ol>
<p>Thanks!</p> | g24929 | [
0.03306230902671814,
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0.00044035897008143365,
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0.036192636936903,
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0.03495553508400917,
0.024273695424199104,
0.048989299684762955,
0.05104982480406761,
-0.0198... |
<p>I've got some data that come from a economic experiment. I'm trying to fit a model using plm() function (plm package). I'm following a very good tutorial (Panel data econometrics in R: The plm package). The only problem is the function allow the following data structure:</p>
<pre><code>individuals / time / x1...xp ... | g410 | [
-0.006916877347975969,
-0.03280482813715935,
-0.004503582138568163,
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0.008773209527134895,
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-0.028278760612010956,
0.02221534214913845,
0.028532935306429863,
-0.01288144662976265,
... |
<p>As the title suggests, I'd like to ask what the difference between using Raw Prices vs. Daily Return vs. Price Ratio in the Augmented Dickey-Fuller unit-root test. The context is that I am trying to find cointegrated pairs of stocks from a given time series in R.</p>
<p>Take a look at these three different resource... | g58082 | [
0.027710597962141037,
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0.019497428089380264,
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0.0789407342672348,
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0.026415150612592697,
0.051612965762615204,
-0.0011413473403081298,
0.04194246232509613,
... |
<p>I am trying to model the volatility of gold using GARCH models and here is the forecast that I obtained.
<img src="http://i.stack.imgur.com/ImrB8.jpg" alt="Gold Volatility"></p>
<p>The plot seems to indicate that the volatility decreases as time passes but I was expecting to see something like an increased volatili... | g58083 | [
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0.013207172974944115,
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0.05956507474184036,
0.05600292608141899,
-0.... |
<p>I have the following data</p>
<pre><code> X black brown
1 women 25 20
2 men 41 44
</code></pre>
<p>How can I see if there is a significant difference in preference between men and women using R</p> | g58084 | [
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0.04144132509827614,
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0.004859854932874441,
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0.049110595136880875,
0.019639985635876656,
... |
<p>What is the best approach to determining variability within different stratums in a survey ?</p>
<p>The easiest approach would be to examine variability over any one response variable, but are there methods to take into account responses across a number of variables.</p>
<p>The objective is to be able to adjust sa... | g58085 | [
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-0.01571688987314701,
0.07195906341075897,
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0.001995051046833396,
... |
<p>I am building a GLS model following protocol in "Zuur, 2009. Mixed effects models..." on p.90. </p>
<p>I have 5 continuous predictors. VarConstPower variance structure works best for me. At first the fixed part of the model includes all covariates. At that point I get the lowest AIC when variance part also includes... | g58086 | [
0.06471355259418488,
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0.015159985981881618,
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0.04361843690276146,
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0.013755472376942635,
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-0.02451893500983715,
0.022540654987096786,
0.004647084977477789,
-0.014025832526385784,
-0... |
<p>I designed an experiment using the fractional factorial design feature in Minitab. Can the results of the experiment be analyzed using something like linear regression and backward selection or is it best to use software that is aware that the experiment is a fractional factorial design experiment?</p> | g41850 | [
0.02694658190011978,
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<p>I am trying to understand how to correctly apply False Discovery Rate when comparing multiple hypothesis tests. Although I use here R code, my doubts are about the procedure, rather than the programming.</p>
<p>I built a toy model in R made of 10000 hypothesis (e.g. genes expression)
made over two 5 samples populat... | g58087 | [
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0.039780452847480774,
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-0.016992252320051193,
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-0.029158955439925194,
0.05580742657184601,
... |
<p>I have made an experiment with 28 subjects. All made the experiments under 3 different conditions (A, B and C). So I have a table like this:</p>
<pre><code>No. A B C
1 3 6 4
2 6 2 6
...
</code></pre>
<p>Now I just want to perform a RM-ANOVA or a Friedman test or a Quade test. That's not the problem.</p>
<p>I ... | g41851 | [
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0.002330812392756343,
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0.015718674287199974,
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0.0013358717551454902,
-0.004250801168382168,
0.023610418662428856,
-0.0212774146348238,
... |
<p>$X\sim N(52,6)$, $Y\sim (40,8)$. What's the standard deviation of $Z=X+Y$?</p>
<p>I'm considering to transform the linear relationship to matrix form
$$Z=\begin{pmatrix}
1& 1\\
\end{pmatrix}\begin{pmatrix}
X\\
Y
\end{pmatrix}$$</p>
<p>and apply $$\Sigma_{z}=A \Sigma^{-1} A'$$</p>
<p>However, I don't know the... | g53 | [
0.026278244331479073,
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-0.03026796132326126,
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0.03802025318145752,
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0.035712968558073044,
-0.02256127819418907,
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0.05712941661477089,
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-... |
<p><strong>Background:</strong> </p>
<p>My professor gave us several copies of his hand-writing handouts last week. Due to the low quality of printer, there are several words in the handouts cannot be recognized. However, I found that I can "<em>guess</em>" what the professor has written on the handouts by reading con... | g58088 | [
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0.01052154041826725,
0.044395823031663895,
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0.007994584739208221,
0.025559978559613228,
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-0.... |
<p>I need to do a data analysis in R. My data consists of 2 populations of animals that have 2 different types of genomes. The children are always born as twins. I also know the mothers' weight and the combined weight of the children after 14 days. I want to fit a model that explains the variability of the twins' weigh... | g12992 | [
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0.0048819840885698795,
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0.029816679656505585,
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0.01391315832734108,
-0.005284623708575964,
-0.0355059951543808,
0.059611689299345016,
... |
<p>I seem to remember from years ago when I first read Bishop's ANN book that it is possible to construct a neural network such that the outputs should represent the posterior probability that I would have found if I used the likelihood approach to separate the same data. Is this true or have I made this up in my mind?... | g41858 | [
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0.016390500590205193,
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0.0332506038248539,
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-0.029007358476519585,
0.01455449964851141,
-0.02194126509130001,
0.012976044788956642,
-0.0... |
<p>I have a class of distributions that I think may have generated some data I have, and would like to find the best fit distribution and corresponding parameters. But the data I have aren't samples from a distribution, they are an empirical PDF. </p> | g770 | [
0.05188755318522453,
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0.017927544191479683,
-0.015593125484883785,
0.03220326453447342,
... |
<p>I had these questions in an exam today. State True or False and explain.</p>
<ol>
<li><p>If k1(.,.) and k2(.,.) are two valid kernel functions, then if h = k1 - k2, is h(.,.) a valid kernel function?</p></li>
<li><p>A standard soft margin SVM is used to classify data set. We have a fixed C parameter. Two different ... | g58089 | [
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0.01953120343387127,
0.05727643519639969,
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0.018032776191830635,
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0.024492988362908363,
0.06864452362060547,
0.02... |
<p>I want to find the correlation between a continous variable with a non normal distribution, positively skewed, and a categorical variable with 4 categories. The only test I can find that fits these variable is the kruskal wallis test, but I am not sure how I can use this test to find the correlation or relationship ... | g58090 | [
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0.02067367173731327,
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0.003145685186609626,
0... |
<p>This question is a follow on from this question - <a href="http://stats.stackexchange.com/questions/70206/correlation-with-non-normal-distribution?noredirect=1#comment135905_70206">Correlation with non-normal distribution</a>. An ANOVA explanation was given here - <a href="http://stats.stackexchange.com/questions/6... | g12998 | [
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-0.0007261987193487585,
0.013694887980818748,
-0.012980002909898758,
0.02519471012055874,
0.0... |
<p>I have the following data:</p>
<pre><code>t mean
147 1.4
143 3
137.5 1.8
133 1.9
129.5 1.8
124.5 2.5
115.5 1.9
107 2.5
102.5 6.3
98.5 6.5
94.5 5
89 5.5
81 4.8
73 9.3
</code></pre>
<p>To me, the slope looks more exponential than linear... | g12999 | [
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0.11068680137395859,
0.00... |
<p>I need to make linear model for which I need to do Gibbs sampling in MCMC simulations. The model needed to be fitted is a linear mixed model. </p>
<p>Please suggest me for a robust R package for this task.</p> | g41864 | [
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<p>I have two regression models and I want to subtract one beta coefficient in model 1 from model2. </p>
<p>Obviously I can just do this on a calculator, but does anyone know of a test I could use in R to test the difference for me, and give me back confidence intervals or standard errors. </p>
<p>I've tried running ... | g13003 | [
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<p>I have been given the pdf:
$$f_{\theta}(x)=\frac{x}{\theta^2}e^{-\frac{x^2}{2\theta^2}}$$
and I want to know if the MLE estimator $\theta$ is unbiased.</p>
<p>Attempt: I want to maximize the function so I take the natural logarithm and then I differentiate with respect to $\theta$ as follows:
$$\frac{d}{d\theta}ln(... | g58091 | [
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0.0068949381820857525,
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0.012468886561691761,
0.05647959187626839,
-0.00... |
<p>[I apologize in advance for the length of this question. but it seems
unavoidable.]</p>
<p>I'm trying to do binary classification, using Bayesian methods, and
I'm having some trouble figuring what methods I need to do so. Bottom
line - I need some kind of decision rule. I've tentatively settled on
a version of the ... | g41866 | [
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0.021730009466409683,
0.07204839587211609,
0.07224535942077637,
0.0200... |
<p>The problem in hand is that the prior distribution which I have received from experts (loan recovery data) ranges from 0 to 100%. Thus a beta distribution was assumed. Where as the actual data shows that loan recovery can be more than 100% due to fees and interest charges. Thus the likelihood function does not follo... | g58092 | [
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0.031745392829179764,
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-0... |
<p>I saw a lot of times claims that they have to be exhaustive (the examples in such books were always set in such way, that they were indeed), on the other hand I also saw a lot of times books stating they should be exclusive (for example $\mathrm{H}_{0}$ as $\mu_1=\mu_2$ and $\mathrm{H}_{1}$ as $\mu_1>\mu_2$) with... | g41869 | [
0.04435501992702484,
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<p>I've 110 variables & 200 data points. Of this 110 variables, one is group variable (say "brown eye","blue eye"). I want to use discriminant analysis to classify the groups based on remaining 119 variables. Since the variables are large, to get a meaningful result I need to reduce the number of variables. So, the... | g58093 | [
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0.00632934644818306,
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0.06445050239562988,
0.03220801055431366,
0.092470... |
<p>I have 2 point clouds (3D points). I can visually tell that the spread in one cloud is much larger than the other, and I have also plotted their error ellipsoids. Now, I'm looking for a statistical test which proves that the the spread is larger in one cloud. </p>
<p>So my question is, if I use a statistical test l... | g58094 | [
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0.009305439889431,
0.035833679139614105,
0.059724580496549606,
-0.03... |
<p>Assume we have a sensor field with dimension M*M. In order to apply any data compression technique, first I want to know what is the compression limit or minimum entropy of the entire sensor field. How could I compute the minimum entropy or compression limit for the sensor field? </p>
<p>or </p>
<p>Actually I want... | g37399 | [
0.002247451338917017,
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0.013467549346387386,
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0.005462974309921265,
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0.021662816405296326,
0.015124023891985416,
... |
<p>All,</p>
<p>I am estimating a multilevel logistic regression with group predictors, but am unclear about some of the advice given by Gelman and Hill (2007) in their book. Therein, they recommend allowing every coefficient to possibly vary, given a large enough N. Does that include group predictors as well? They ... | g41880 | [
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0.031606268137693405,
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0.029646946117281914,
0... |
<p>For example, the random forest algorithm is not especially susceptible to "over-tuning" because it has 1 hyperparameter, "mtry," and mtry typically does not have a large influence on the result of the algorithm.</p>
<p>On the other hand, I imagine the "knn" algorithm is prone to "over-tuning", as it's hyperparamete... | g58095 | [
0.008697176352143288,
0.03901302441954613,
0.003758758772164583,
0.02758019044995308,
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0.007206111215054989,
0.006514572538435459,
0.023077717050909996,
0.016698172315955162,
... |
<p>I am trying to predict the sales conversion using proc logistics in SAS. Right now I have around 3 months of data, and it will gradually grow to more than an year over time. My intuition is that the most recent data is a better predictor of the event, and hence I want to weight the data using the exponential weighti... | g58096 | [
0.07663100957870483,
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0.0027242139913141727,
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0.03156089782714844,
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0.08980607241392136,
... |
<p>For a Poisson regression we can model exposure $\epsilon_i$ in observation $Y_i$ as $Y_i \sim Poisson(\epsilon_i*\lambda)$.</p>
<p>For instance, in a Poisson regression, if we observe:</p>
<p>$y = \begin{bmatrix} 2 & 3 & 4 & 5 \end{bmatrix}$</p>
<p>With exposures $\epsilon = \begin{bmatrix} 2 & 1 ... | g58097 | [
0.01089110504835844,
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0.013817177154123783,
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0.021139977499842644,
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-0.027745015919208527,
-0.04665862396359444,
0.024369865655899048,
0.015808727592229843,
... |
<p>Which test should I apply for measuring change in proportions and means when I have same primary sampling units but different respondents in two waves of longitudinal survey? Should I apply McNemar's test for proportion and dependent-samples t test for means, or which test to study the difference between two waves? ... | g58098 | [
0.010283629409968853,
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0.00708895456045866,
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0.032890237867832184,
0.01751047745347023,
-0.004296313971281052,
0.02... |
<p>When a black ball is drawn, it is not replaced in the set, but white balls are replaced.</p>
<p>I have thought of this, with the notations: </p>
<ul>
<li>$b$, $w$ the initial number of black and white balls</li>
<li>$x_i = (b - i)/(b + w - i)$ </li>
</ul>
<p>The probability of drawing a black ball $Pb(n)$ after n... | g58099 | [
-0.0033154443372040987,
0.05063270777463913,
0.004449347034096718,
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0.013443383388221264,
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0.014095611870288849,
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0.0008858490036800504,
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0.036235976964235306,
0.006315495353192091,
... |
<p>I have three variables (sample size is mentioned below), and I want to analyze data using regression models as recommended by Judd and Kenny (1981) to see if $cc$ mediates the relationship between $spdm$ and $cty$ (I'm using abbreviations; see below for variable names). I have a unequal sample size problem, and I do... | g58100 | [
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0.006899022497236729,
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0.049866992980241776,
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0.009353420697152615,
-0.007652563508599997,
-0.003988778684288263,
0.019702862948179245,
... |
<p>I am trying to fit a mixture model containing a gamma and an exponential distribution:</p>
<p>The general form, using the pdfs, is: p * gammapdf + (1-p) * exponentialpdf. </p>
<p>The pdfs for the Gamma and Exponential, respectively are as follows:</p>
<p><img src="http://i.stack.imgur.com/iVv1O.png" alt="Gamma PD... | g13018 | [
-0.01620250940322876,
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0.008347610011696815,
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0.0018379560206085443,
0.014061025343835354,
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0.0378454215824604,
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0.03134404122829437,
0.03709082305431366,
0.003933935426175594,
0.056671686470508575,
-0.0... |
<p>If I have a population of 5000, statistics suggests that I need to sample about 350+ to get a confidence interval of 95% with margin of error 5%.</p>
<p>So why do I see that sometimes we can get away with as low as 30?! That seems so much lower than what all these tables and calculators suggest.</p> | g13019 | [
0.0650184154510498,
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0.01528784167021513,
0.015163087286055088,
0.0056837997399270535,
-0.0... |
<p>I am attempting to fit a Cox proportional hazard model to my data. I think I have the formula correct but am having trouble understanding the output. I have tried looked through the documentation and it is hard for me to understand. Any help would be greatly appreciated, thank you!</p>
<p>The formula:</p>
<pre>... | g58101 | [
0.04741273820400238,
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0.034560296684503555,
0.000043744472350226715,
0.016678553074598312,
0.05670730397105217,
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-0.03465723618865013,
-0.0003600100171752274,
0.04517632722854614,
0.08562912791967392,
-0.... |
<p>Given a set of features vectors $X=\{\vec{x}_1,..,\vec{x}_n\}$, binary ground truth data $Y=\{y_1,..,y_n\}$ and continuous prediction $\bar{Y} = \{\bar{y}_1,..,\bar{y}_n\}\in [0,1]$, I want to perform some regression analysis to estimate a function $f(\vec{x}_p) \approx e_p$ where $e_p = abs(y_p - \bar{y_p})$. </p>
... | g13021 | [
-0.011204789392650127,
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0.04391969367861748,
0.029944660142064095,
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-0.01837744191288948,
0.0012155954027548432,
0.08089116215705872,
0.006621827371418476,
0.024... |
<p>I'm taking a statistical learning class, and I need to brush up on my calculus. I already took calculus and probability several years ago, but I have a bad memory.</p>
<p>Are there any good books or general resources that give a review of calculus with a probability and statistics slant? I noticed that most calculu... | g4 | [
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0.020868433639407158,
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0.03469064459204674,
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-0.0188049... |
<p>I would like to know how do you determine the performance of your models. That is, if you fit a multinomial logit or probit model for un-ordered discrete choice. What do you use to evaluate whether you have a good model? </p>
<p>Please provide me with any reference material that I could read more on this topic. We... | g58102 | [
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0.06992031633853912,
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<p>I have an unbalanced panel data set, which covers a set of about 10 variables I am very interested in as controls in a regression. However, only a few of these variables are available in all waves: most of them are only available for a few waves down to two which are only available for 5 waves. Additionally, these v... | g58103 | [
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0.029216626659035683,
0.024048851802945137,
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0.012625512667000294,
-0.031043244525790215,
0.004597900900989771,
0.008329044096171856,
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... |
<p>I remember something from a stats course many years ago which might be helpful now. I want to distinguish between patients who show symptoms all over the board, vs. patients who have similarly high sum-scores, but due to a few very high symptoms. Symptoms have a scale from 0 to 3. </p>
<p>I remember the following p... | g58104 | [
0.006138706114143133,
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0.02541804313659668,
0.07897542417049408,
... |
<p>I'm trying to fit a multivariate (i.e., multiple response) mixed model in <code>R</code>. Aside from the <code>ASReml-r</code> and <code>SabreR</code> packages (which require external software), it seems this is only possible in <code>MCMCglmm</code>. In the <a href="http://www.jstatsoft.org/v33/i02/" rel="nofollow"... | g37720 | [
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0.05932462587952614,
0... |
<p>Basic setup: </p>
<p>regression model: $y = \text{constant} +\beta_1x_1+\beta_2x_2+\beta_3x_3+\beta_4x_4+\alpha C+\epsilon$
where C is the vector of control variables.</p>
<p>I'm interested in $\beta$ and expect $\beta_1$ and $\beta_2$ to be negative. However, there is multicollinearity problem in the model, the c... | g58105 | [
0.013333122245967388,
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0.0007050224230624735,
0.019442664459347725,
0.023863766342401505,
0.02224074862897396,
0.0297... |
<p>I have been asked to try to operationalize our research question methodologically in an experimental design but since this is my first experience doing so I feel unsure and am looking for some help. We are looking at reputation systems (such as that of eBay) where provision of rewards and/or sanctions can stabilize ... | g58106 | [
0.014737567864358425,
0.05419766530394554,
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-0.030... |
<blockquote>
<p>We have an exponential distribution $$f(x)=\frac{e^\frac{-x}{\theta}}{\theta}$$</p>
<p>We are told that $n=3$ and that the data are given as
$x_1=1, x_2=2.5, x_3=5.5$</p>
<p>a.) Determine an approximate 95% confidence interval based on asymptotic normality of $\overline{x}$</p>
<p>b.... | g13024 | [
0.01367077138274908,
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0.021035341545939445,
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0.011781708337366581,
0.0007896845927461982,
0.05060676857829094,
0.034309376031160355,
-0.00... |
<p>I have the following distribution, defined for $0 < x < \theta$, its value is $0$ otherwise.</p>
<p>$$f_\theta(x)= \frac{2x}{\theta^2} $$</p>
<p>Find the MLE of $\theta$</p>
<p>I tried:</p>
<p>$$\prod_{i=1}^n \frac{2}{\theta^2}x_i =\left(\frac{2}{\theta^2}\right)^n \prod_{i=1}^n x_i $$</p>
<p>Taking the n... | g13025 | [
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-0.03290374204516411,
-0.024198809638619423,
0.012105986475944519,
0.033133525401353836,
... |
<p>We’ve run a mixed effects logistic regression using the following syntax;</p>
<pre><code># fit model
fm0 <- glmer(GoalEncoding ~ 1 + Group + (1|Subject) + (1|Item), exp0,
family = binomial(link="logit"))
# model output
summary(fm0)
</code></pre>
<p>Subject and Item are the random effects. We’re get... | g58107 | [
-0.03190535679459572,
-0.060903772711753845,
0.013354124501347542,
0.0004735311958938837,
0.011495057493448257,
0.033656004816293716,
0.03406721353530884,
-0.0063906325958669186,
-0.03305022418498993,
-0.04709953814744949,
0.003919726703315973,
0.0015213008737191558,
0.025199009105563164,
... |
<p>My task is to identify parameters (mean, standard deviation, height) of gaussian peaks in given histogram data with as lowest CV as possible. Number of peaks and approximate means are known (pointed by user).</p>
<p>Standard approach uses regression to fit gaussian mixture to the data. Results are listed below:</p>... | g58108 | [
0.04209611564874649,
-0.035948384553194046,
-0.025036362931132317,
0.00043625556281767786,
0.012261958792805672,
-0.011846810579299927,
0.03460434451699257,
-0.030207138508558273,
-0.024054912850260735,
-0.010678899474442005,
-0.010129104368388653,
0.04713832587003708,
0.07318907976150513,
... |
<p>I ran into (what I think is) an inconsistency when running a random-intercept model (using the <em>lmer</em> function in the <em>lme4</em> package in R).</p>
<p>Here is what I do: I first run a model with a set of covariates; then I run the same model re-scaling (linearly transforming) one of the regressors. To my ... | g58109 | [
-0.012701086699962616,
-0.06373297423124313,
-0.0016741062281653285,
-0.004130290821194649,
0.0552351139485836,
-0.023048128932714462,
0.04198085516691208,
0.01745154894888401,
-0.06477775424718857,
-0.0007035069284029305,
-0.03852998465299606,
0.05780671909451485,
0.027583250775933266,
-0... |
<p>In the fully Bayesian approach, the predictive distribution is:</p>
<p>$$ P( Y|X ) = \int P(\theta | X ) P( Y | \theta ) d\theta $$</p>
<p>When the integral is difficult to compute, we might resort to the Maximum Likelihood approach, and approximate the predictive distribution as follows:</p>
<p>$$ P( Y|X ) \appr... | g58110 | [
0.030300751328468323,
-0.008030576631426811,
0.0040862369351089,
0.009887916035950184,
-0.052190251648426056,
-0.03188108280301094,
0.020319407805800438,
0.05753367766737938,
-0.060751352459192276,
-0.007105283904820681,
0.023590991273522377,
-0.029243214055895805,
0.05776810646057129,
0.0... |
<p>Does anyone know how to derive the Variance of Bin Zhou's volatility estimator (Theorem 1) in 'High-Frequency Data and Volatility in Foreign-Exchange Rates' (1996)?</p>
<p><a href="http://public.econ.duke.edu/~get/browse/courses/201/spr11/DOWNLOADS/MicroStructure/Zhou-JBES-1996.pdf" rel="nofollow">PDF Link</a> atta... | g58111 | [
0.0419343076646328,
-0.0003751887707039714,
0.0021983713377267122,
-0.018167510628700256,
0.03801450505852699,
-0.024426111951470375,
0.034357067197561264,
-0.0013125973055139184,
0.00814279355108738,
-0.02393725886940956,
-0.04220081865787506,
0.03205416351556778,
-0.07186201959848404,
-0... |
<p>I am reading a paper by Tom Minka and trying to follow the steps to perform the updates for the Expectation Propagation algorithm. I am having trouble getting the initialisation of the posterior distribution going. So, the first step involves writing out your joint distribution as a product of factors. In my case, I... | g58112 | [
0.030342109501361847,
-0.09123597294092178,
-0.027249962091445923,
-0.07376068085432053,
-0.03354284167289734,
-0.01988649182021618,
0.011028628796339035,
0.026644611731171608,
-0.03639201447367668,
0.016150247305631638,
-0.011939139105379581,
0.026249347254633904,
0.021875912323594093,
-0... |
<p>I have to analyze if a network (represented as a graph) mantains its connectivity over the time. The data that I've obtained from the simulation is given <a href="http://pastebin.com/cpk0hQBU" rel="nofollow">here</a>, where L1 points out the vertex of the graph, and the column <code>value</code> stands for the degre... | g13028 | [
-0.010897709988057613,
0.0035962772089987993,
-0.009672772139310837,
-0.04274209588766098,
0.04508000984787941,
-0.0823109820485115,
0.043853696435689926,
-0.057400088757276535,
-0.05854808911681175,
-0.005088161211460829,
-0.0021834787912666798,
0.04156814515590668,
0.03158852458000183,
0... |
<p>Assume you draw $N$ values from a bounded set, say $[0, 1]$ without loss of generality.</p>
<p>If I am right, the centered values $X-m$ will remain in range $[{1\over N}-1, 1-{1\over N}]$ (by considering the most imbalanced 0/1 cases). And the standard deviation in range $[0,{1 \over 2}]$ (even $N$) or $[0,{1\over ... | g13033 | [
0.005919634830206633,
-0.008321193978190422,
-0.013695244677364826,
-0.0060416157357394695,
0.0015193009749054909,
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0.0053246053867042065,
-0.040369004011154175,
-0.027082888409495354,
0.005360076669603586,
0.0092390393838286... |
<p>I found one formula to calculate the pairwise distance between samples according to their SNPs in the following paper: Siu, Jin and Xiong, <a href="http://www.plosone.org/article/fetchObject.action?uri=info%3adoi/10.1371/journal.pone.0029901&representation=PDF" rel="nofollow">Manifold Learning for Human Populati... | g58113 | [
-0.02473665401339531,
-0.012479187920689583,
-0.014337458647787571,
-0.030447740107774734,
-0.0367623008787632,
0.0033398238010704517,
-0.010716970078647137,
0.04446224868297577,
-0.04514695331454277,
0.00981015432626009,
-0.013109639286994934,
-0.001312857959419489,
0.05585389956831932,
-... |
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