question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have an extremely simple question regarding chi-square test. So far I have found two different formulas for it:
$$
\chi^2=\sum\frac{(x_o-x_e)^2}{x_e}
$$
and
$$
\chi^2=\sum\frac{(x_o-x_e)^2}{\sigma^2}
$$</p>
<p>$x_o$ is the observed data while $x_e$ is the expected data. Clearly the two formulas do not return the ... | g67685 | [
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<p>First of all, sorry for the huge pictures, but I'm in desperate need of some input and help on the results following a study. I'm trying to interpret the results from my study, but I can't quite figure out what causes some of the positive correlations to turn into negative coefficients in the regression analysis.</p... | g67686 | [
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<p>I'm working with unbalanced panel data using time and firms as IDs and would like to find out how to test for correlation between two panel equations that may be seemingly unrelated.</p>
<p>The second question is about any package that allows the use of a Heckman selection model for panel data in Stata.</p> | g27305 | [
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<p>I am learning the smoothing spline method. I saw that smoothing spline is a penalty term to reduce overfitting in linear regression. Given dataset {$(x_1,y_1),(x_2,y_2)..(x_n,y_n)$}So the formular such as:
$$RSS=\sum(y_i-f(x_i))^2+\lambda\int((f(t)'')^2dt$$</p>
<p>Assume it is linear case so
$$f(x_i)=ax_i+b$$
$$f(... | g76 | [
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<p>To my surprise I found that standard errors and thus Wald confidence intervals became smaller when I removed the intercept from a simple logistic regression model, using <code>glm()</code> and R.</p>
<pre><code># load an object named "my.df" to the global enviroment
load(url("http://hansekbrand.se/code/test.RData")... | g67687 | [
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<p>I am interested in estimating the effect of security S on crime C in a given city over time (eight quarters) for twenty cities, so it's panel data. The problem is, instead of actual security spending I have two imperfect measures of S, call them S1 and S2. These were collected independently from each other but in bo... | g67688 | [
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<p>I have a bunch of curves that look like <a href="http://en.wikipedia.org/wiki/Sigmoid_function" rel="nofollow">S-curves</a> <em>(stored in a db with Point format)</em> and I am interested in finding this midpoint between both horizontal asymptotes for each of them. So, if <strong>X-axis</strong> represents <strong>t... | g67689 | [
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<p>When people talk about the 80-20 rule in the context of wealth, it is usually expressed, verbally, by stating that the 20 percent of the people with the highest wealth get 80 percent of the wealth, and the top 20 percent of the richest 20 get 80 percent of that, or 64% of total wealth, and so forth. Then there is ha... | g67690 | [
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<p>The following figure shows the log-likelihood of individual observations for different subsets of a data set - the horizontal line shows the average log-likelihood:</p>
<p><img src="http://i.stack.imgur.com/14O5r.png" alt="figure one"></p>
<p>So, the first subset includes all the data points observed up to t=7, th... | g67691 | [
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<p>Can anyone explain how Stata computes the least squares parameters with a single explanatory variable - what algorithm Stats uses to compute the parameters. </p>
<p>Actually I want to understand the computational algorithm of negative binomial regression model.</p> | g27310 | [
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<p>I conducted a panel OLS regression using gretl, on a balanced panel with around 25 zones and 10 time periods. I would like to use the model to forecast future values of y (dependant variable), given known future changes of x (explanatory variable).</p>
<p>I would like to ask: how to deal with (a) the constant, (b) ... | g67692 | [
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<p>I have tried to reproduce some research (using PCA) from SPSS in R. In my experience, <a href="http://www.personality-project.org/R/html/principal.html"><code>principal()</code></a> function from package <code>psych</code> was the only function that came close (or if my memory serves me right, dead on) to match the ... | g48000 | [
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<p>There have been a few questions about statistical <a href="http://stats.stackexchange.com/questions/tagged/textbook">textbooks</a>, such as the question <a href="http://stats.stackexchange.com/questions/170/free-statistical-textbooks">Free statistical textbooks</a>. However, I am looking for textbooks that are Open ... | g27315 | [
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<p>I'm trying to use JAGS for clustering mixtures of multivariate normal distributions. In order to model different covariance structures in each cluster I wanted to use one big (C*D)xD matrix (C - number of clusters, D - number of dimensions) which would represent all of the covariance matrices stacked one upon anothe... | g48005 | [
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<p>I have a set of 76 annual occurrences of $x$ and $y$. When I run a linear regression, $y$ is significantly correlated to $x$. The Durbin-Watson test shows $y$ is also serially correlated.</p>
<p>My goal is to predict $y$ from a certain future $x$ and to determine the prediction interval.</p>
<p>I believe the pro... | g67693 | [
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<p>Let $\{X_i\}_n$ be a sequence of $n$ random variables independently and identically drawn from either $P$ or $Q$. Thus the sequence $\{X_i\}_n$ has a product distribution, which is either $P^n$ or $Q^n$. Assume that $P$ and $Q_\theta$ have the same support $\Omega$.</p>
<p>Suppose that the <a href="https://en.wik... | g41899 | [
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<p>$\DeclareMathOperator{\var}{Var}$
<a href="http://stats.stackexchange.com/questions/15423/how-to-compute-prediction-bands-for-non-linear-regression">How to compute prediction bands for non-linear regression?</a></p>
<p>In the above link, you have mentioned about the variance-covariance matrix of the estimates. What... | g67694 | [
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... |
<p>The question:</p>
<blockquote>
<p>Find a 99% confidence interval for the difference in mean oxygen
consumption of an algae that is in 100% concentrated seawater with
algae that is not in 100% seawater (i.e., 50% or 75%).</p>
</blockquote>
<p>Is this the correct approach?</p>
<blockquote>
<p>If we let $X_1... | g27319 | [
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<p>The minimum variance, unbiased estimator $\hat \theta$ of $\theta$ is defined by
$$\hat \theta = \text{argmin}_{\hat \theta} \; \mathbb{E} \left( (\hat \theta - \theta)^2 \, | \, \theta\right), \quad \text{ subject to } \quad \mathbb{E} \left( \hat \theta \, | \, \theta\right) - \theta = 0 $$
where the expectation,... | g39874 | [
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... |
<p>Let $A$, $B$, $C$ be random variables.
$A$ and $B$ are not independent
$A$ and $C$ are independent.
$B$ and $C$ are independent.</p>
<p>Are $A$ and the product $BC$ independent?
This is, is $E[ABC]=E[A]E[BC]=E[A]E[B]E[C]$??</p> | g67695 | [
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<p>I am trying to understand the relation between observed power and p-value in <a href="http://stats.stackexchange.com/a/59288/1005">Stephane's reply</a>, which I think is based on J. M. Hoenig and D. M. Heisey (2001) "The Abuse of Power: The Abuse of Power Calculations for Data Analysis," The American Statistician 5... | g13054 | [
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<p>Basically, right now I am trying to do some nearest-neighbour searching on an approach where I don't have points in Euclidean space. To do a nearest-neighbour search currently, I take the query and compare it (with a special similarity function) to each model in the database to find the most similar one. </p>
<p>... | g41927 | [
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<p>As an entrepreneur you try to find a model of your business. If you simulate this via Monte Carlo you could see sensitive areas in e.g. the marketing strategy and how it affects e.g. sales.
I like to think of it as a prediction device. My intuition is that a simulation allows for "what if" questions in a way shorte... | g41930 | [
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<p>I have 52 samples daily, weekly and biweekly data for 3 subjects over the course of a 10 month period. At two points during the 10 month period the resolution increases to daily samples as the people begin taking a supplement. I have been considering a percentage of supplement that is (total supplication/total all s... | g67696 | [
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<p>I am a law student researching which factors influence the CSR (corporate social responsibility, <code>GSE_RAW</code>) behavior of companies. As my studies didn't offer any statistics courses, I'm having trouble to understand what type of statistical analysis I should perform on my data. After describing the data, I... | g67697 | [
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<p>I have an assignment that asks me to explore different series of data with respect to the effects that an incinerator built in 1981 in Massachusetts, has on the price of houses in that area.</p>
<p>I have around 30 different sets of data with regards to the houses ranging from 'number of bathrooms', 'distance from ... | g27328 | [
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<p>In Steven Pinker's book <a href="http://rads.stackoverflow.com/amzn/click/0670022950">Better Angels of Our Nature</a>, he notes that</p>
<blockquote>
<p>Probability is a matter of perspective. Viewed at sufficiently close
range, individual events have determinate causes. Even a coin flip can
be predicted from... | g67698 | [
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<p>I'm working on a questionnaire that is intended to measure two constructs. There are presently 26 items in the questionnaire -- eleven for construct 1 and 15 for construct 2 -- and each item has five available responses: "strongly disagree" "disagree" "neutral" "agree" "strongly agree".</p>
<p>In our first iterati... | g32046 | [
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<p>Here is a section of <em><a href="http://www.cs.ubc.ca/~murphyk/MLbook/pml-print3-ch19.pdf" rel="nofollow">Machine Learning: a Probabilistic Perspective</a></em> by Kevin Patrick Murphy</p>
<p><img src="http://i.stack.imgur.com/jatxV.png" alt="enter image description here"></p>
<p>I don't understand in (19.18) why... | g27330 | [
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<p>I'm having trouble understanding how certain combinations of random variables can correlate. The problem is as follows:</p>
<p>I have a binary $m \times n$ matrix $A$ of full rank (over the finite field $\mathbb{F}_2$ with two elements), where each row has exactly $w$ $1$'s (i.e., their weights are all $w$).</p>
<... | g67699 | [
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0.03912520781159401,
-0.0017174516106024384,... |
<p>I have <strong>some dependent variables</strong> related to the growth of a company having categories like (e.g. for variables indicating net profit, financial turnover etc.) </p>
<p>(1) decreasing, </p>
<p>(2) stable, </p>
<p>(3) increasing and </p>
<p>(4) rapidly increasing.</p>
<p>Now these variables are <st... | g49782 | [
-0.00776296854019165,
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0.0017010236624628305,
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-0.016661280766129494,
0.038589268922805786,
0.044894713908433914,
0.057124603539705276,
... |
<p>I have two arrays of 2D points and I need to estimate their correlation. What formula should I use? Thank you.</p>
<p>Example of arrays:</p>
<p>X: [[1,5],[2,5],[1,7],[4,1]]</p>
<p>Y: [[3,4],[1,6],[4,6],[4,3]]</p> | g67700 | [
0.06968545913696289,
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0.01595229096710682,
0.0... |
<p>If I am right, you can calculate eta-squared in an ANOVA by:</p>
<p>SS (covariate of interest) divided by SS (total)</p>
<p>I was wondering if the calculation and interpretation is the same in a General Linear Model (GLM).</p> | g27331 | [
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0.02839890494942665,
0.011564400978386402,
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0.07260376214981079,
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<p>I have a data set that is essentially of the form of a sequence of pairs:</p>
<p>$$\left(\cap T_i, P'(W|\cap T_i)\right)$$</p>
<p>The sequence might have duplicate $\cap T_i$'s with different $P'(W|\cap T_i)$'s (where $P'$ denotes an empirical probability). The events $T_i$ are not independent. I would like esti... | g67701 | [
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0.0... |
<blockquote>
<p>is there any research into or applications of machine learning in number theory? </p>
</blockquote>
<p>am also looking for (leading examples of) statistical/empirical analysis of number theory questions. also wondering if genetic algorithms in particular have ever been used in these areas. </p>
<ul>... | g67702 | [
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0.002133072353899479,
0.024512574076652527,
0.09166320413351059,
0.03... |
<p>I have a dataset of measurements (non-normally distributed).
Each line of this dataset is composed by two measurements of the same variable in a specific time (i.e. XYY [time, meas1, meas2]). This dataset contains 24 lines.</p>
<p>Is it correct to use Wilcoxon Signed-Rank Test to compare these two measurements? Is ... | g67703 | [
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0.0007194055942818522,
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0.... |
<p>I am trying to understand a linear model obtained with <a href="http://svmlight.joachims.org/" rel="nofollow">SVMlight</a>. The model file contains a number of support vectors and their corresponding $\alpha_i y_i$. Since all $y_i \in \lbrace -1,+1 \rbrace$, I know that $\alpha_i = |\alpha_i y_i|$. </p>
<p>From the... | g27334 | [
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0.... |
<p>In ELISA</p>
<p>Is it necessary to obtain true concentration level of antibodies for diagnosis? </p>
<p>Is there a model allowing us to do so? I know there is a 4-parameters logistic model, but will people conducting tests use it?</p>
<p>How about other test, like NAA test? </p> | g67704 | [
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-... |
<p>this is my first post on Cross Validated so I apologize in advance if I'm not yet familiar with any conventions regarding forum posts.
Currently, I'm working on a feature selection task using elastic net in caret and I would like to visualize the feature importance for each model trained in each cross validation ste... | g27335 | [
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0.017046481370925903,
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0.0... |
<p>When running a model with a categorical predictor, the output contains n-1 p.values where n is the number of levels in the factor. One level is taken to be the reference group.</p>
<p>For example: I observed plants in different environments and want to know if the substrate1, substrate2 and substrate3 (categorical ... | g67705 | [
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<p>I have a sequence of events for a number of users. Now I want to see if there is any correlation or a likelihood score between two consecutive events. For example, I have 10 types of events (A1,A2,A3,A4,A5,A6,A7,A8,A9,A10) and the time between two consecutive events. Now I want to find out how likely it is (or what ... | g67706 | [
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<p>I have been reading over some statistics notes, and certain things are introduced without motivation (note: I am a mathematician and not a statistician, so my stats knowledge is woefully inadequate, so I know little about the motivation). One of these oddly-introduced things is Spearman's correlation coefficient. So... | g27337 | [
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<p>We have conducted an experiment using a two-alternative forced-choice task where listeners must indicate whether they prefer the sound quality of an auditory stimulus in interval A or interval B. These preference judgments are made for different types of signal processing, which are randomized. We have three signa... | g67707 | [
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<p>I am making a web-app that is supposed to help people memorize Japanese kana symbols using <a href="http://en.wikipedia.org/wiki/Flashcard" rel="nofollow">flashcard</a>. How it works at the moment is that on each new flashcard, user is presented with one symbol which gets chosen randomly from a pool of X symbols. Us... | g67708 | [
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<p>I've a dataset of 120 samples in a 10-fold cross validation setting.
Currently, I pick the training data of the first holdout and do a 5-fold cross-validation on it to pick the values of gamma and C by grid search. I'm using SVM with RBF kernel.
Since I'm doing a ten 10 cross-validation to report precision,recall, ... | g27342 | [
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0.029741300269961357,
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<p>What type of test would fit my data in this situation?</p>
<p>I'm measuring a count variable. Like in a zero-inflated poisson, I have numerous observations that are zeros because of a separate process. But I also have observations that have extremely high outcomes in the count variable because of a distinct process... | g67709 | [
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0.013514755293726921,
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... |
<p>I am using COX PH model to fit a lifetime data set and estimating parameters. By the by I am also simulating data and trying to find out estimates of parameters. Now I want to calculate bias and standard deviation to determine the size of the bias How can I do it? Can anybody give me suggestions and some articles na... | g27345 | [
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<p>I am really having trouble understanding the intuition behind autocorrelation. I mean why are we even calculating a correlation of some series with itself? Can anybody explain it in lay terms with an everyday example from life? </p>
<p>Also, I see that while calculating the ACF, we have to take lags. But how does ... | g67710 | [
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<p>I'm doing an education study and I'm trying to see the effect of website usage on quiz scores in a class of college students. There were 30 students in the class and they took 10 weekly quizzes over the course of the semester. They also had a website where they could log in and use a study tool. The website kept ... | g27346 | [
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... |
<p>I was wondering if there was a specific name for this formula and if it is involved in an established statistical process (like how chi-squared tests are for comparing observation classes or t tests are for distributions without a known population stddev), or if this is an original development from the referenced ar... | g44543 | [
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<p>I have sales data which records at what time (by second) and how many were sold. Therefore, the data is count data with around 90-150 sales during a 3-day period. If I agggregated it to the 10 minute interval, I will have around 75% zero observations because for example 100/(24*3*6) = 0.2314815. But I think this is ... | g67711 | [
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<p>I have a large dataset (tens of thousands of predictors) on which I would like to perform feature reduction with the intent of better model-building for prediction. Deep Belief Networks seem to address the problem in such a way that they produce an output that bears some resemblance to that of PCA, i.e. a series of ... | g67712 | [
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<p>The R function <code>read.csv</code> works as the following as stated in the manual: "If there is a header and the first row contains one fewer field than the number of columns, the first column in the input is used for the row names." That's good. However, when it comes to the function <code>write.csv</code>, I can... | g67713 | [
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<p>I am working on a project in which I am using several independent variables to "predict" the values of an outcome using linear regression.</p>
<p>In R this is done quite simply as</p>
<pre><code>model <- lm(outcome ~ predictor1 + predictor2 + predictor3)
fitted <- model$fitted.values
</code></pre>
<p>I am ... | g27349 | [
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<p>I have collected data on gas fluxes from plots of soil subjected to 5 different treatments ("D2", "K2", "M", "N", and "O2"), which also possessed variable clay contents. The experiment was laid out in a randomized complete block design, with 4 replications. Within each plot, two separate measurements of flux were ... | g67714 | [
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0.00705825537443161,
0.04340866208076477,
-... |
<p>I am trying to understand Mixture Markov Models in order to cluster a set of sequences that do not necessarily all have the same states occurring in them. </p>
<p>If I have several sequences that I am trying to fit a Mixture Markov Model to, how do I go about the fact that some of the chains contain a part of all p... | g67715 | [
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0.013363339938223362,
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0.0472041592001915,
0.016... |
<p>I have a model with a binary dependent variable (DV) and 5 independent variables, all of which are matched (each person, twice).</p>
<p>I think since these matched INDEPENDENT variables can be considered "repeated-measures", <em>generalized estimating equations</em> (GEE) is the best approach here. However, I have ... | g27353 | [
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<p>I would like to compare two measurements of a variable (anxiety) on the same subjects at different times. I was planning on using the paired samples t-test in SPSS, but I believe the variables are ordinal, since the questions were scaled 0,1,2,3. How can I compare them?</p> | g67716 | [
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... |
<p>I have done behavioral experiments,and have no clue even how to start making statistics on the data.</p>
<p>Here is the description of the experiment:<br>
Mice are subjected to an experimental task where they have to distinguish stripe patterns of various contrasts and width. It is known that at a certain spatial f... | g67717 | [
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<p>I think I am confused with this thing. </p>
<p>If we have a 3 dimension Gaussian then the MLE estimate for $\mu$ is a vector with 3 element</p>
<p>$$\mu(1)' = \frac{1}{n}\sum_{j = 1} ^ n x_j\text{ and so on }\mu(2)\text{ for }y\text{ and }\mu(3)\text{ for }z$$</p>
<p>also $\sigma$</p>
<p>$$ \sigma(1)' = ... | g67718 | [
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... |
<p>I have annual temperature data from a variety of weather stations in the Caribbean and I want to be able to show statistically that the trends for each station are significant, either positive or negative or no trend. </p>
<p>I can obviosly plot the data and fit a line, but I want to make a stronger argument tha... | g67719 | [
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0.07349349558353424,
0... |
<p>I have a set of count data that I have fitted both a linear model to and a Poisson generalized linear model. The mean of the raw data is 233.375 and the standard deviation 279.983. I have been surprised when I fit a Poisson glm in R that the intercept = 5.53865. A negative bionomial glm in R gives an intercept of... | g67720 | [
0.04918677359819412,
-0.027625221759080887,
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0.014491568319499493,
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-0.025653991848230362... |
<p>Suppose I have a study of 3031 people that obtains responses to various questions (95% CL). One of the questions (Q1a) gets a yes response from 616 of the people. Of those 616, only 34 have a QualityB (the remaining 582 don't) that is dependent on a yes answer to (Q1a).</p>
<p>When determining the margin of error ... | g67721 | [
0.029828907921910286,
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0.015136467292904854,
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0.05702131241559982,
0.008947882801294327,
0.021128863096237183,
... |
<p>I have a philosophical question regarding omitted variable bias.</p>
<p>We have the typical regression model (population model)
$$
Y= \beta_0 + \beta_1X_1 + ... + \beta_nX_n + \upsilon,
$$
where the samples are from $(Y,X_1,...,X_n)$, and then a bunch of conditions by which the OLS estimates behave quite well.</p>... | g67722 | [
0.017956221476197243,
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0.01918927952647209,
0.04597178474068642,
0.012296493165194988,
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0.04... |
<p>I have a question regarding the interpretation of the whiskers of a boxplot. I have read the following: "On the top and bottom of
the rectangle, the “whiskers” show the range of 1.5 times the distance between the
0.25- and 0.75-quantiles"¨, but do not entirely understand what is meant with "distance".</p>
<p>It can... | g67723 | [
0.016761917620897293,
0.026376625522971153,
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0.013428245671093464,
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-0.03213886171579361,
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0.055115584284067154,
... |
<p>So we have arithmetic mean (AM), geometric mean (GM) and harmonic mean (HM). Their mathematical formulation is also well known along with their associated stereotypical examples (e.g., Harmonic mean and it's application to 'speed' related problems).</p>
<p>However, a question that has always intrigued me is "how do... | g27363 | [
0.006773029454052448,
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0... |
<p>I have a data set that's 200k rows X 50 columns. I'm trying to use a <code>knn</code> model on it but there is huge variance in performance depending on which variables are used (i.e., <code>rsqd</code> ranges from .01 (using all variables) to .98 (using only 5 variables)).</p>
<p>This kind of compounds my problem... | g67724 | [
-0.0314677357673645,
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0.003389249090105295,
0.005498285870999098,
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0.0038803943898528814,
0.01606210134923458,
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-0.028895672410726547,
0.02514551766216755,
0.0460028275847435,
0.039530713111162186,
0.02... |
<p>I'm trying to obtain an estimation of the uncertainty related to an analytical method:
my function is just a linear regression $f: y=ax+b+ \epsilon$ with $y_i=\frac{R_i}{C}$, both $R$ and $C$ are affected by a measured uncertainty, $s_R$ and $s_C$ respectively.</p>
<p>I want to calculate the total uncertainty with ... | g67725 | [
-0.0008094095974229276,
0.00767081743106246,
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0.026123514398932457,
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0.05058363825082779,
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-0.02780282497406006,
0.0692935436964035,
0.008435196243226528,
... |
<p>Suppose I've got an 80/20 split between modeling/validation observations. I've fit a model to the modeling data set, and I'm comfortable with the error that I'm seeing on the validation data set. Before I roll out my model for scoring future observations, is it appropriate to combine the validation back with the mod... | g27368 | [
0.014079911634325981,
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0.0047851381823420525,
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0.03003563918173313,
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-0.019771747291088104,
0.03657464683055878,
0.012214739806950092,
0.04980050027370453,
0.0... |
<p>I want to fit a linear model of $y$ on $x$ with respect to a grouping factor and with respect to a covariance structure for the dependent variable within groups. I have a dataset similar to the following:</p>
<pre><code>y1 <- rnorm(25)
y2 <- y1 + rnorm(25)
y3 <- y2 + rnorm(25)
y4 <- y3 + rnorm(25)
y <... | g67726 | [
-0.025578664615750313,
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0.06433993577957153,
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-0.006214343011379242,
0.016404196619987488,
0.018026204779744148,
-0.007329338230192661,
-... |
<p>Regarding fitting a Weibull two parameters probability density function (pdf), with the <code>fitdistr</code> from MASS package, in R:</p>
<p>1 - What is the iteration algorithm/method used for scale and shape Maximum Likelihood Estimation (MLE)?</p>
<p>I used to think it was Newton-Raphson, but after looking <a h... | g27370 | [
0.06331527233123779,
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0.0011031732428818941,
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0.01433898601680994,
0.03833119571208954,
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0.05334443598985672,
-0.04613953456282616,
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0.10890605300664902,
0.07145... |
<p>I have this (I think) simple problem, which I guess is just a generalization of the Chernoff bound to Bernoulli schemes. Assume I have a bowl with N balls with R different colors. The balls are not necessarily evenly distributed. How many balls do I need to sample (with replacement) in order to decide with confidenc... | g67727 | [
0.02862253598868847,
0.02527088299393654,
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0.06526800990104675,
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0.018573325127363205,
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0.0391... |
<p>I am running a Market Mix model. There is a general practice in the industry to create an ad stock variable for media variables (like TV). I came across polynomial distributed lag model. I was thinking to used polynomial distributed lag instead of creating Adstock variables. Can anyone tell me whether should I move ... | g67728 | [
0.02938731014728546,
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0.03975553810596466,
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0.04986640810966492,
0.03865622729063034,
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0.0168... |
<p>I am reading an old article on Information Value Theory and to properly understand the material, I need to get my head around the following inferential concept where <strong><em>u</em></strong>, <strong><em>v</em></strong> are random variables and <strong><em>S</em></strong> is the state of information.</p>
<blockq... | g67729 | [
0.03891393542289734,
0.032332535833120346,
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0.04047813639044762,
-0.01981557533144951,
-0.02169077657163143,
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0.04592389613389969,
0.00433899974450469,
-0.01018150057643652,
-0.009592670947313309,
0.016302261501550674,
0.023018423467874527,
0.000... |
<p>I'm wondering why in Generative learning algorithm, they try to maximize the probability</p>
<p>$\prod_{i=1}^np(x^{(i)}, y^{(i)})$</p>
<p>While in Discriminative learning algorithm, it is</p>
<p>$\prod_{i=1}^np(y^{(i)} | x^{(i)})$</p>
<ol>
<li><p>What is the reason of maximizing these terms?</p></li>
<li><p>Why ... | g67730 | [
0.0306955948472023,
0.01101713441312313,
0.018416667357087135,
0.041764140129089355,
0.05894098058342934,
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0.014680534601211548,
0.035741038620471954,
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-0.0004705011087935418,
-0.06320768594741821,
0.061476558446884155,
0.07643898576498032,
0.034089... |
<p>In R, usually one performs a generalized additive model like so:</p>
<pre><code>library(mgcv)
x <- gam(depvar ~ s(indvar1) + s(indvar2) + parametricvar)
</code></pre>
<p>Say I want to explore the non-parametric interaction of <code>indvar1</code> and <code>indvar2</code>.</p>
<p>Is the following kosher? Are th... | g49528 | [
-0.04346858710050583,
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0.018215853720903397,
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0.004589930176734924,
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0.0434233732521534,
0.... |
<p>Given an ARMA model and a historical time series, I'm trying to create a set of $n$ forecast scenarios, where each scenario $s$ is a potential future hourly time series $x_s[t]$, with a given probability, $p_s$. I'm familiar with how to generate an ARMA point forecast for a given horizon - how do you extend this the... | g38158 | [
0.0017933804774656892,
0.0161232128739357,
0.013497555628418922,
0.007053580600768328,
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0.028700023889541626,
0.0006053298711776733,
-0.02776772528886795,
0.008392130956053734,
0.04... |
<p>I am working with some data that has been classified by domain experts. However, the classification they use is not 100% accurate. How can I deal with data that may not be correctly classified?</p>
<p>Are there any models which are more resilient to data that are not classified with 100% accuracy? Does such a class... | g37826 | [
-0.008935850113630295,
-0.024006474763154984,
0.009296712465584278,
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0.04054214805364609,
0.031670015305280685,
0.01811343990266323,
0.02225026860833168,
0.005510871298611164,
-0.026343122124671936,
0.04006627947092056,
0.013128302991390228,
0.07771722972393036,
-0.03... |
<p>This question is a follow up to <a href="http://stats.stackexchange.com/questions/24595/how-to-correctly-treat-multiple-data-points-per-each-subject">the question I asked yesterday</a>. </p>
<p>Here is the current situation again. I have data for a within subject measurement, where each variable is measured repeate... | g27378 | [
0.010647664777934551,
-0.03469885140657425,
0.009624408558011055,
-0.04742325097322464,
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0.03531039506196976,
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-0.000681391335092485,
-0.007003321778029203,
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-0.029943622648715973,
... |
<p>Suppose blood pressure is a continuous outcome variable and you run a linear GEE with following predictors: age (years), weight (lbs), and smoking (yes/no). How would you interpret the coefficients for these predictors? Would it be the same as in "regular" linear regression?</p> | g67731 | [
0.008340292610228062,
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0.0013045279774814844,
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0.060281381011009216,
0.019327437505126,
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-0.05764983221888542,
0.020572246983647346,
0.02175169438123703,
0.021431492641568184,
-0.04... |
<p>I want to estimate the parameters that minimize a multivariate function with noise based on realized observations.</p>
<p>As a simple example, say I have observed the univariate sample below:</p>
<p><img src="http://i.stack.imgur.com/drzJH.png" alt="enter image description here"></p>
<p>The samples were generated... | g40355 | [
0.0707794576883316,
-0.0742533802986145,
-0.0060702539049088955,
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0.01909792609512806,
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0.02307969518005848,
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-0.0301863644272089,
0.05859200283885002,
0.0328... |
<p>I'm having an argument with a colleague (neither of us have a strong statistical / research methods background) on whether we should randomize questionnaire layout.</p>
<p>The survey in question is a feedback forms on teacher performance which are distributed for high school pupils. So one pupil gets up to 20 surve... | g27381 | [
-0.003925866447389126,
0.0215486828237772,
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0.11079622060060501,
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0.007064661011099815,
0.0... |
<p>I have two years of data which looks basically like this:</p>
<p>Date <strong><em>_</em>__<em></strong> Violence Y/N? _</em> Number of patients</p>
<p>1/1/2008 <strong><em>_</em>___<em></strong> 0 <strong></em>__<em>_</em>__<em>_</em>____</strong> 11</p>
<p>2/1/2008 <strong><em>_</em>__<em>_</em></st... | g27382 | [
0.04469757899641991,
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0.014808840118348598,
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0.05513414368033409,
0.02309555374085903,
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-0.07392202317714691,
0.0468137226998806,
0.00547837233170867,
0.0572708398103714,
-0.03656994... |
<p>I have two time series, series1 and series2. My aim is to find <strong>how much Series2 is different from Series1, automatically/quantitatively</strong>.<br>
Image can be seen in its original size by <a href="http://img713.imageshack.us/img713/3401/image001eg.gif" rel="nofollow">clicking here</a>.
<img src="http://i... | g67732 | [
0.0029253249522298574,
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0.02729865163564682,
0.03641119971871376,
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0.032157447189092636,
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0.031902119517326355,
0.031516965478658676,
-... |
<p>I have a certain confusion. I refer to this <a href="http://arxiv.org/pdf/0903.5463v3.pdf" rel="nofollow">paper</a>.</p>
<p>Let's say I have $p$ variables $x_1, x_2, \dots, x_p$ which follow a multivariate Gaussian distribution. Now suppose I have $N$ examples or samples from this distribution. However, some of the... | g67733 | [
0.0331147126853466,
-0.04150611534714699,
-0.016107574105262756,
-0.051851093769073486,
0.004498861264437437,
0.029085449874401093,
0.004936256445944309,
0.004110770765691996,
-0.009186020120978355,
0.016983071342110634,
-0.03359946236014366,
0.034983791410923004,
0.03674841672182083,
0.04... |
<p>Please see <a href="http://stats.stackexchange.com/questions/3708/forecasting-unemployment-rate">question</a> for the background.</p>
<p>Following the advice of @kwak and @Andy W, I have decided to use the package <strong>plm</strong> in <code>R</code> to fit my model. Here an excerpt of the data <code>df</code> (t... | g13358 | [
0.0061960844323039055,
-0.03633852303028107,
-0.02658992074429989,
-0.02475603111088276,
0.006705212406814098,
0.027922023087739944,
0.05139488726854324,
0.061341650784015656,
-0.01667344942688942,
-0.03063591942191124,
0.003984082955867052,
0.042108550667762756,
0.03952475264668465,
-0.02... |
<p>I have two averages +/- strandard deviations of left ventricular mass before and after of physical activity.
Before physical activity, left ventricular mass is 150 +/- 20 grams
After physical activity, left ventricular mass is 120 +/- 10 grams
The left ventricular mass percentage variation, after physical activity ... | g67734 | [
0.016774659976363182,
-0.03111823834478855,
-0.00006996216689003631,
0.006413430906832218,
-0.006554532330483198,
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0.05924583598971367,
0.022384466603398323,
-0.010532505810260773,
-0.052747733891010284,
-0.01731053739786148,
-0.027429819107055664,
0.028694214299321175,... |
<p>Are there any tools that can format and write to external file output of principal component analysis in Stata? </p>
<p>I'm thinking about something that will work in similar vein to [excellent] family of <a href="http://repec.org/bocode/e/estout/index.html" rel="nofollow">estout</a> commands.</p> | g67735 | [
-0.007779277395457029,
-0.03566985949873924,
0.019194019958376884,
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-0.020294204354286194,
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0.025725945830345154,
0.017905713990330696,
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-0.02403591386973858,
0.06319554150104523,
0.04000598564743996,
0.07198069244623184,
-0.02... |
<p>This may be a basic question, but I was wondering why an $R$ value in a regression model can simply be squared to give a figure of explained variance?</p>
<p>I understand that $R$ coefficient can give the strength of a relationship, but I don't understand how simply squaring this value gives a measure of explained ... | g38159 | [
0.016424529254436493,
0.008917657658457756,
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0.03329584747552872,
0.0033276104368269444,
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0.038287851959466934,
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-0.0630994439125061,
-0.019550487399101257,
0.03433700650930405,
0.032008249312639236,
0.008... |
<p>I have two sets of data, and I want to know if the second set is sufficiently different from the first to be considered different.</p>
<p>More specifically, I have a sample set A from a number of pixels in the vicinity of point X in an image, and another sample B of pixels in the vicinity of point Y in the same ima... | g37566 | [
0.018244164064526558,
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0.006140456069260836,
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0.04230865463614464,
0.06380610167980194,
0.04932299256324768,
-0... |
<p>1) How to find important features in RandomForest classifier (in sklearn) with high statistical significant?</p>
<p>2) The input data I have is unbalanced which I simply repeat data to compensate that. When I do shuffling, some of these repeated data go to training and some goes to test which definitely increase th... | g27389 | [
-0.042562324553728104,
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0.005531656555831432,
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0.04294874891638756,
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0.03518315777182579,
0.058506693691015244,
... |
<p>I am using a survival model to predict membership counts. Other than predicting signups that are being added, we are trying to use a coxph model to predict accounts that will get canceled.</p>
<p>In our problem, there are two types of "deaths" that can happen. The company can terminate the account because the cus... | g11392 | [
-0.004110885784029961,
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<p>I am looking for some open source or an existing library I can use. As far as I tell the glmnet package isn't very easily extensible to cover the non negative case. I may be wrong, Any one with any ideas much appreciated.</p>
<p>By non-negative I mean that all coefficients are constrained to be positive (> 0).</p> | g27391 | [
-0.008803839795291424,
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0.022837191820144653,
0.03681949898600578,
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... |
<p>Are there any well-known results/tools/literature on using bagging and random feature subset selection for regression or SGD-based methods? </p> | g27393 | [
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... |
<p>I have 46 replicate trees I sampled in a 2 year study.
My objective is: To estimate the proportion of variation among-trees w/in year, and proportion variation due to among year and tree interaction.</p>
<p>Response: 12, 15, 32, 42, 13, 26, 10, 15</p>
<p>Year: A, A, A, A, B, B, B, B,</p>
<p>Tree: 1, 2, 3, 4, 1, ... | g48073 | [
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... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/9664/what-are-examples-where-a-naive-bootstrap-fails">What are examples where a “naive bootstrap” fails?</a> </p>
</blockquote>
<p>Perhaps this question will turn out to be a bit soft, but I th... | g49783 | [
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0.066... |
<p>I have 2 groups, each containing 20 individuals. For each individual I have a dissimilarity matrix of a number of judged items. I'd like to evaluate whether there is an overall difference between the groups in the semantic networks underlying their judgements. As a first step, I computed 2D MDS spaces for each group... | g48075 | [
-0.040339525789022446,
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0.... |
<p>Am looking for pointers to publicly(online) available high-dimensional regression datasets for evaluating my research work. </p>
<p>By high-dimensional, am looking for regression datsets with the number of predictor variables (features) ranging anywhere from 50 to 2000.</p>
<p>Most of the regression datasets on st... | g67736 | [
-0.008430070243775845,
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-... |
<p>In an experiment with continuous-value random variable, e.g. measuring length of cucumbers. I would like to compare the probability of getting a particular length range in two different conditions. e.g. $P1=P(0.1<L<0.2, fertilizer A)$, $P2=P(0.1<L<0.2, fertilizer B)$.</p>
<p>So I create 2 histograms for... | g27397 | [
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0.045... |
<p>On the website for CRF++ <a href="http://crfpp.sourceforge.net/" rel="nofollow">http://crfpp.sourceforge.net/</a>
they mention that marginal probabilities can be output for each possible label.
My question is, in CRF theory, what's the formula for this marginal probability? I think it's:</p>
<p>$$p_{_\theta}(Y_{_j}... | g27400 | [
-0.0018220600904896855,
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0.... |
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