question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I'm trying to analyse some data from a set of bird surveys. My response variable is "bird abundance", which is the number of birds counted over a five-minute period. These five-minute counts were conducted at ~200 sites. Counts were repeated three times at each site, although there are ~20 sites where only two count... | 72,102 |
<p>I have the vectors of co-ordinates of the grid points $(x, y)$ and the joint probability values, $z$. Could you recommend a way to do marginalization for the below joint distribution? (In my problem, I have random sampled grid points from the joint distribution. Of course, if the points were lined up on straight lin... | 72,103 |
<p>Suppose we have ordinal data that can assume the following values: $0$, $1$, $2$, $3$ and $4$. Also suppose that there are a lot of data points that fall into category $1$. Can we use zero inflated Poisson regression to model this?</p> | 44,953 |
<p>Basically I have </p>
<ul>
<li>Four groups (2-by-2) with sample means $\overline{x_{1,A}}$, $\overline{x_{2,A}}$, $\overline{x_{1,B}}$ and $\overline{x_{2,B}}$, standard deviations $s_{1,A}$, $s_{2,A}$, $s_{1,B}$ and $s_{2,B}$ with sample sizes $n_A$ and $n_B$ (i.e. $n_{1,A}=n_{2,A}$ and $n_{1,B}=n_{2,B}$).</li>
</... | 72,104 |
<p>EDITED: I want to select the a regression model (geographically weighted regression vs. OLS) based on a pseudo-R2 comparing the predicted values and the actual ones. I am aiming to regress the predicted values onto the actual values. My models have a logged response variable. My questions are as follows:</p>
<p>1) ... | 16,171 |
<p>The main <strong>problem</strong> is: I cannot obtain similar parameter estimates with EViews and R.</p>
<p>For reasons I do not know myself, I need to estimate parameters for certain data using EViews. This is done by picking the NLS (nonlinear least squares) option and using the following formula: <code>indep_va... | 33,907 |
<p>I have a sequence of binary data, each row of which has seemingly random bits and associated with an integer value ("<em>rank</em>"). When we have a binary datum, we always can calculate the <em>rank</em> related to it but not the data <em>from</em> it's rank value. For an example, with 32-bit length and sorted by i... | 33,911 |
<p>How do I explain Generalized Methods of moments and how it is used to a non statistician? </p>
<p>So far I am going with it is something we use to estimate conditions such as averages and variation based on samples we have collected.</p>
<p>How do I explain the part where you estimate the parameter vector by minim... | 72,105 |
<p>In clustering methods such as <a href="http://en.wikipedia.org/wiki/K-means_clustering">K-means</a>, the euclidean distance is the metric to use. As a result, we only calculate the mean values within each cluster. And then adjustments are made on the elements based on their distance to each mean value. </p>
<p>I wa... | 72,106 |
<p>I have recently become proficient at using <code>Python/scipy</code> <code>curve_fit</code> to perform linear regression. However, with higher order polynomials my data is sometimes overfits. </p>
<p><strong>How can I add regularization to reduce over-fitting?</strong></p> | 72,107 |
<p>My lecturer's regression:</p>
<pre><code>Variables:
*lprice*, the log of house prices
*y81*, which is a dummy for the year 1981 against 1978
*ldist*, log of distance from incinerator to houses
</code></pre>
<p><strong>These are comments made by my lecturer to help give context:</strong></p>
<blockquote>
<ul>
... | 72,108 |
<p>Given a data set with a continuous outcome variable $Y$ and two nominal IV $X_1$ and $X_2$ which have 4 (A,B,C,D) and 3 (E,F,G) levels respectively, we can assign the first level of each as a reference level and create dummy or indicator variables:</p>
<p>$X_1: X_1B$ , $X_1C$ , $X_1D $</p>
<p>$X_2: X_2F$ , $X_2G$<... | 72,109 |
<p>I thought that the loadings in factor analysis were the correlations between the observed variables and the latent factors. However, when I do factor analysis in R using the psych package, this does not seem to be the case:</p>
<pre><code> library(psych)
set.seed(1)
X <- matrix(rnorm(200), ncol=10)
... | 72,110 |
<p>What's the difference between "probability of H given E" as calculated by Bayes theorem and the "positive predictive value" of E?</p> | 33,914 |
<p>I am trying to get a grip on pattern recognition with discrete data. Currently I started to work through the classics of Duda and Hart. Is there something you could recommend particularly for applied use, preferably with R. Is there even a useR Springer book I haven't found yet or any other good tutorial? Something ... | 72,111 |
<p><strong>Conditioning a point process is the concept being investigated in this post.</strong> The marked point processes are of interest.
Figure <strong>A</strong> demonstrates a phenomenon being investigated for modelling. We recognize a feature such can be modeled by a point as the center and an angle (Figures <st... | 33,916 |
<p>I have a dataset as follows:</p>
<p>ni-xi 76 48 38 19 20 14 26 29 39 45 38 36 32 34 26 21 23 12 24 18 14 61 35 21 32 20 89 30 34 35</p>
<p>xi 0 0 16 26 1 8 23 19 24 16 16 19 0 0 0 6 8 3 5 9 5 0 34 17 13 0 1 11 13 22</p>
<p>I want to model this dataset as a beta-binomial distribution: xi ~ Binomi... | 33,918 |
<p>I'm working with Hidden Markov Models and I have a dataset composed by independent phrases, where each word is an observation. Hence, the best way to adjust my parameters (via Baum-Welch algorithm) is considering each phrase per time and not all phrases concatenated.</p>
<p>I would like to know if there is an algor... | 72,112 |
<p>To keep it simple, I have sets of data in which I have a control and a treated sample. The data I obtain is "yes" or "no" (0 or 1) for a particular behaviour. I have 150 data points for each condition (150 for control, 150 treated), obtained across 3 experimental runs, which I intend to pool. They are not paired in ... | 72,113 |
<p>I am having trouble figuring out how to group data using the inter-quartile ranges calculated with a box and whiskers plot as well as looking at Tukey's Hinges. I understand the IQR and Tukey's hinges are not the same thing and that there are different interpretations of Tukey's Hinges. Basically, I did a calculatio... | 72,114 |
<p>As far as I know, I have two options for tests in linear regression. The $F$-test for the model (if it explains more variance than it has error variance) and the $t$-test (to see if the slope is not zero). With more than one predictor, I can see why both tests are there. But in my case, I only have one predictor. In... | 72,115 |
<p>In Ackley and Hinton's paper <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.154.1370&rep=rep1&type=pdf" rel="nofollow">"A Learning Algorithm for Boltzmann Machines"</a>, they write that </p>
<blockquote>
<p>A hidden unit would be needed, for
example, if the environment demanded
that... | 33,920 |
<p>You probably know the trick in the movie <a href="http://www.imdb.com/title/tt0482571/" rel="nofollow">The Prestige</a> :</p>
<p><strong>[MOVIE SPOILER]</strong> A magician has found an impressive magic trick: he goes into a machine, close the door, and then disappears and reappears in the other side of the room. B... | 33,922 |
<p>This is more a general question on machine learning in general, but I have two datasets ~75k rows of patients and 100 columns (call it <code>training</code> and <code>testing</code>)--each column is either a numeric predictor corresponding to how many times they've visited a specific physician, or a factor (two exam... | 16,248 |
<p>Quite simple, I have some probability distribution p(x), how can I measure whether one empirical density (set of delta masses) is a better approximation than another. I know that KL-divergence is a well accepted measure between two continuous densities, but it's not clear how to apply that to a set of samples.</p> | 72,116 |
<p>After asking 16 questions (yes or no) to 75 people I have a table of their answers coded like <code>00110011110101010</code> ('0'=no and '1'=yes). Now I would like to find groups of people who answered in the most similar way (ideally to find all possible groups with similitudes from 16/16 to 12/16).</p>
<p>How to ... | 72,117 |
<p>I was reading online, and I found that</p>
<p>If the Variance of X increases then the value of R-squared increases</p>
<p>If the Variance of the residuals increases then the value of R-squared decreases</p>
<p>Can someone explain the intuition behind these two statements.</p>
<p>I am generally confused about the... | 72,118 |
<p><img src="http://i.stack.imgur.com/jgduc.png" alt="Binned Residual Plot"></p>
<p>My binned residual plot is quite strange looking, the 95% confidence lines are so very jagged, with points between. I have colored this "inside" of the 95% confidence interval because it is really hard otherwise to tell which points a... | 72,119 |
<p>When would the rejection sampling method be preferred to the inverse CDF method for sampling truncated random variables?</p>
<p>And when would the inverse CDF method be preferred to the rejection sampling method for sampling truncated random variables?</p> | 72,120 |
<p><strong>Background</strong></p>
<p>I have a generative model for a process that can be described as follows:</p>
<p>$$
y = t(x, w) + e
$$</p>
<p>where $x$ and $y$ observations of a set of random variables which are related by a non-linear transformation function $t$, parameterised by the unknown parameters to be ... | 72,121 |
<p>I've got a dataset where I'm attempting to predict when an individual will develop a particular disease based on a set of biomarkers. I'm able to find a pretty good fitting model, but it has a high degree of heteroskedasticity. However, this heteroskedasticity is expected--it makes sense that the model will have sma... | 205 |
<p>I wonder what differences are between t-test and ANOVA in linear regression?</p>
<ol>
<li>Is a t-test to test whether any one of the slopes and intercept has
mean zero, while ANOVA to test whether all slopes have mean zero? Is this the only difference between them?</li>
<li>In simple linear regression i.e. where th... | 33,926 |
<p>I want to fit an ex-Gaussian distribution (which has three parameters: $\mu$, $\sigma$, and $\nu$) to reaction time data.</p>
<p><strong>How many data points are needed as a minimum to reasonably fit this distribution?</strong></p>
<p>I am aware that an answer to this question depends on many factors (e.g., how mu... | 72,122 |
<p>Here, "weight of evidence" (WOE) is a common term in the published scientific and policy-making literature, most often seen in the context of risk assessment, defined by:</p>
<p>$$w(e : h) = \log\frac{p(e|h)}{p(e|\overline{h})}$$</p>
<p>where $e$ is evidence, $h$ is hypothesis.</p>
<p>Now, I want to know what is ... | 33,927 |
<p>Suppose $X \sim \mathcal{N}(\mu_x, \sigma^2_x)$ and $Y \sim \mathcal{N}(\mu_y, \sigma^2_y)$</p>
<p>I am interested in $z = \min(\mu_x, \mu_y)$. Is there an unbiased estimator for $z$?</p>
<p>The simple estimator of $\min(\bar{x}, \bar{y})$ where $\bar{x}$ and $\bar{y}$ are sample means of $X$ and $Y$, for example... | 72,123 |
<p>Having worked mostly with cross sectional data so far and very very recently browsing, scanning stumbling through a bunch of introductory time series literature I wonder what which role explanatory variables are playing in time series analysis. </p>
<p>I would like to <em>explain a trend</em> instead of de-trending... | 72,124 |
<p>I am wondering how to generate uniformly distributed points on the surface of the 3-d unit sphere? Also after generating those points, what is the best way to visualize and check whether they are truly uniform on the surface $x^2+y^2+z^2=1$?</p> | 44,979 |
<p>Can we do that? If yes, then what are the conditions which should be met? Thanks.</p> | 72,125 |
<p><img src="http://i.stack.imgur.com/upzR9.jpg" alt="enter image description here"></p>
<p>In ques 5, I have 10 factors which could affect purchasing decision. Now i wanted to find the co-relation between 10 factors which i will treat as Independent factors and Purchase decision which i intend to use as a dependent v... | 72,126 |
<p>I've been stuck on this problem for several days: In a sample of size $I$, each sample member $i=1,\ldots,I$, is described by some feature $m(i)$. Value $B$ is a certain function of $\mbox{avg}(m(i))$, that can be approximated by: $B=1/\mbox{avg}(m(i))$. Now I have to analyze the following expression:
<img src="http... | 72,127 |
<p>Imagine you have a set of four elements (A-D) with some numeric values of a measured property (several observations for each element):</p>
<pre><code>A: 26 25 29 21
B: 24 17 16
C: 32 34 29 19 25 27 28
D: 23 29 26 20 14
</code></pre>
<p>I have to detect if there are significant differences on the average levels. So... | 72,128 |
<p>I have a number of rasters of environmental data (~10) which may be important predictors for modelling species presence and abundance at ~10 different locations.</p>
<p>I would like to know which of the rasters are important in explaining the variance in observed results. Is it appropriate to look for principal com... | 44,982 |
<p>I am working with abiotic soil data such as bulk density, moisture levels and soil chemistry as response data (some quantitative some as percentages) and a mix of abiotic and biotic data as environmental data. To compare different sites I want to use multivariate statistics. For this PCA is an accepted method in thi... | 72,129 |
<p>I have a large set of data points of the form (mean, stdev). I wish to reduce this to a single (better) mean, and a (hopefully) smaller standard deviation.</p>
<p>Clearly I could simply compute $\frac{\sum data_{mean}}{N}$, however this does not take in to account the fact that some of the data points are significa... | 49,455 |
<p>I am working on a magnetic-resonance imaging dataset which includes about 100 observations (= subjects) and 20000 predictors (=voxels). I would like to conduct classification in R using methods like support-vector machines or random-forests. I believe that analysis of large datasets will require special setup &... | 12,481 |
<p>Which distributions are their own Fourier transform besides the <em>normal distribution</em> and the <em>generalized arcsine distribution</em>?</p> | 33,938 |
<p>Let's say I have a list of 100 MLB pitchers and 5 statistics for each of them. The difference between, for example, an ERA of 3.5 and 3.1 might not look like a lot to a naive similarity algorithm, but is a lot in baseball. Given that a lot of the player statistics that I'm looking at have this little variance, a lot... | 72,130 |
<p>I need simple example of ARIMA model, that performs forecasting on a small time series set e.g., (x1,y1), (x2,y2), (x3,y3), (x4,y4), (x5,y5), (x6,y6)</p>
<p>I found many definitions from various places… but I couldn't find a solved example.</p> | 49,888 |
<p>Select $n$ numbers without replacement from the set $\{1,2,...,m\}$, and generate the set $S=\{a_1,a_2,...,a_n\}$. I want to calculate the expectation of the variance for the sampling set $\mathbb{E}[Var(S)]$ and the maximum variance among all samples : $\max{Var(S)}$.</p>
<p>Besides, what's the distribution of the... | 33,941 |
<p>I have read from <a href="http://www.r-tutor.com/elementary-statistics/logistic-regression/estimated-logistic-regression-equation" rel="nofollow">here</a> and understand how to calculate the estimated logit from a fitted logistic regression model, but how to work on the confidence interval? As it involved a variance... | 37,568 |
<p>I just wanted to make sure I'm right here. I have a situation where I need to prove that on days where we sell more than 10 items, our margin (sale price vs. suggested price) goes up. I'm not really sure it's possible to prove this, but this is what I'm working with. </p>
<p>The table at the top is an itemized list... | 18,591 |
<p>I'm trying to understand how Principal Component Analysis and Factor Analysis work by
implementing examples. Although I'm mainly using Python and Numpy here, this isn't Python-specific, as I'd like to know how to get the correct result generally speaking.</p>
<p>There is an example in chapter 16 of <a href="http://... | 72,131 |
<p>How to create three dimensional matrix? For example:</p>
<p>A = matrix 4 * 5 (4 rows, 5 columns)</p>
<p>B = matrix 4 * 10 (4 rows, 10 columns)</p>
<p>How to turn these two matrices a three-dimensional matrix?</p> | 72,132 |
<p>I am admittedly doing homework, but two problems are worded in such a way that is confusing me. Part (b) asks, "Determine the probability that an individual who has saved for retirement has saved less than $50,000. Use relative frequencies."</p>
<p>Part (c) asks, "Determine the probability that a randomly chosen in... | 72,133 |
<p>A simplified explanation with the focus on the following questions is being inquired. Appreciation goes in advance to whom provides <strong>scientific</strong>--<strong>simple</strong>--<strong>practical</strong> explanation.<br>
Having an area <strong>A</strong> enveloping <strong>N</strong> number of points the de... | 33,946 |
<p>I have a rudimentary question regarding how to "normalize" a set of time series data, and would appreciate your thoughts.</p>
<p>To make it very simple, the hypothetical situation is as follows:
Suppose we have the products A and B, both of which are of similar nature and functions and can be used as a substitute ... | 18,592 |
<p>I admittedly am horrible at statistics. I know that the probability of an individual who has saved for retirement has saved less then 50,000 USD is 16.4% according to my sample data, but only 69% of workers say they have saved for retirement. So what is the probability for a random person selected from the entire po... | 44,993 |
<p>Given a collection of $(x,y)$ data, one might do a non/semiparametric regression of $y$ on $x$ to understand how to predict the $E(Y|X)$. Similarly, if one has enough data, it might be useful take a narrow vertical slice of the data (a small range of $x$), and try to understand the pdf of $Y$ at that point. Howeve... | 37,956 |
<p><img src="http://upload.wikimedia.org/math/8/d/e/8def8df3d62ea70cbf10a6e2b2b3127a.png" alt="regression"></p>
<p>I'm trying to see why this is the case. I have taken the LHS and added $X\hat{\beta}$ and subtracted $X\hat{\beta}$.</p>
<p>From this I can get both terms on the right but I end up with a cross product ... | 72,134 |
<p>I am familiar with the chi-squared goodness of fit test and also the chi-squared test of independence. An example of the chi-squared goodness of fit is where we have frequencies for three different groups and want to know if the observed proportions differ from the expected proportions. An example of the chi-squared... | 72,135 |
<p>I'm looking for a good introductory book/course on Support Vector Machines.</p>
<p>My statistical background is almost non existent, so the more introductory the better.</p> | 72,136 |
<p>I have some doubts about the following exercise:</p>
<p>Given the sequence of Bernoulli (0,1/2) independent random variables $x(n)$, $n\ge 1$, determine the average function and autocorrelation (time-delay) of the process:</p>
<p>$z(n)=\sum_{m=1}^n y(m),\quad n\ge1$</p>
<p>with $y(m)=2x(m) -1 $</p>
<p>for signif... | 72,137 |
<p>I now have two averaged numbers, say $a$ and $b$.</p>
<p>$a=1.1$ with 95% Confidence Interval of $\pm0.2$ and $b=1.0$ with 95% Confidence Interval of $\pm0.1$.</p>
<p>Is it reasonable to calculate their percentage difference w.r.t $b$ as
$$\%\ diff=\frac{1.1-1.0}{1.0}=10\%$$</p>
<p>From my understanding, due to t... | 72,138 |
<p>Before fitting a linear mixed model, can any plots be used to show a random intercept/slope is justifiable in the model? I.e. these plots may indicate a different pattern for each individual over time.</p>
<p>After fitting a linear mixed model, what diagnostics can be performed to see if any model modification is n... | 72,139 |
<p>I need to find gamma fit for data in Python 3.2.</p>
<pre><code>param = gamma.fit(samp) // samp is a list of floating point numbers
</code></pre>
<p>I got error: <code>TypeError: cannot perform reduce with flexible type</code>
Any help would be appreciated.</p> | 72,140 |
<p>I have got 10k data of the form <code>(y, x1, x2)</code> where <code>y</code> is the dependent variables and <code>x1, x2</code> are independent variables.</p>
<p>I have an existing model <code>M</code>, where <code>M(x1, x2)</code> gives the pdf of <code>y</code>. So <code>M(x1,x2,y)</code> gives the density at <c... | 72,141 |
<p>I want to fit an ARMA model on a time series (quarterly log returns of a 10 year bond) using MATLAB R2012b. This is part of an exercise.</p>
<p>I have problems with the code and the interpretation of a result.
This is the code I'm using:</p>
<pre><code>% last element is the most recent one, first element is the ol... | 33,950 |
<p>I just stumbled upon a wiki article:</p>
<p><a href="http://en.wikipedia.org/wiki/Endogeneity_(economics)#Omitted_Variable" rel="nofollow">http://en.wikipedia.org/wiki/Endogeneity_(economics)#Omitted_Variable</a></p>
<p>In the section "simultaneity" theres a description of a model which says that both variables ar... | 72,142 |
<p>In linear models we need to check if a relationship exists among the explanatory variables. If they correlate too much then there is collinearity (i.e., the variables partly explain each other). I am currently just looking at the pairwise correlation between each of the explanatory variables.</p>
<p><strong>Questio... | 12,486 |
<p>I am reading a paper in which a statistical difference has been found between two treatment groups for a variable A (p=.05), but not for variables B (p=.06) and C(p=.06), even though A=B-C. Is this possible, and if so, how? The paper states that "All data were statistically analyzed using the Student's independent t... | 41,968 |
<p>Assume we would fit this model with <code>systemfit()</code> from the <a href="http://cran.r-project.org/web/packages/systemfit/" rel="nofollow">systemfit</a> R package.</p>
<p>$y = \beta_1 x + \gamma_1 z + u$</p>
<p>$z = \beta_2 w + \gamma_2 y + v$</p>
<p>Now I can get an estimate of $Cor(u,v)$.</p>
<p>I know t... | 72,143 |
<p>A simplified regression equation $ES=\frac{a+b}{n_1+n_2}$ has been suggested as an alternative to Egger's regression equation $\frac{ES}{SE}=\frac{a+b}{SE}$, where ES=Effect Size, $n_1$=sample size of the patients, $n_2$=sample size of the controls, SE=Standard Error.</p>
<p>This alternative test, that was presente... | 72,144 |
<p>Suppose I have 2 variables</p>
<p>$A$:<br>
$P(A) =$ 0.01<br>
$P( \lnot A) =$ 0.99</p>
<p>And $B$ that depends on $A$:</p>
<p>$P(B|A) =$ 0.05<br>
$P( \lnot B|A) =$ 0.95<br>
$P(B| \lnot A) =$ 0.01<br>
$P( \lnot B| \lnot A) =$ 0.99 </p>
<p>Applying:
$$P(B)=\sum_{A}^{ } P(B|A)P(A)$$ </p>
<p>we get
$P(B)=(0.01)(... | 45,906 |
<p>A pathologist friend came to me for help with the following question for a research project. The goal is to compare the effectiveness of three different diagnostic techniques. The data set is as follows: there are 50 different specimens, each specimen was evaluated by 4 pathologists, and 3 different instruments (i... | 72,145 |
<p>I am trying to predict real estate sales prices. </p>
<ul>
<li>In my dataset there are independent variables that are both nominal and numeric (square meters, prices etc.) </li>
<li>Before feeding the data to any regression algorithm I'd like to preprocess it correctly (binning, normalizing mean / std deviation, di... | 33,959 |
<p>My question is regarding the interpretation of the percent of deviance explained (and other $R^2$ anaologs or pseudo $R^2$ values for GLMs.</p>
<p>Is this a meaningful summary statistic for models other than Gaussian? That is, is it at least as meaningful/useful as the $R^2$ statistic in the typical OLS regression... | 49,889 |
<p>Imagine that you have access to a collection of studies in which an age range, a sample size and an "effect" (say, cigarettes per day) is reported. What is the best way to construct a meta-regression of cigarettes per day by age?</p>
<p>The hard part here is to correctly interpolate across these studies with diffe... | 45,014 |
<p>I am relatively new to non-parametric models, such as the Hierarchical Dirichlet Process, Pitman-Yor processes, etc. but I have read that non-parametric methods are <em>data-driven</em>, and that they can be more <em>robust</em> than their parametric counter-parts. I am looking for evidence and an exposition of why ... | 33,962 |
<p>I was wondering: is there are a package in R for automated <a href="http://en.wikipedia.org/wiki/Autoregressive_conditional_heteroskedasticity#GARCH" rel="nofollow">GARCH</a> model selection? I'm thinking of something like what the <a href="http://cran.r-project.org/web/packages/forecast/index.html" rel="nofollow">... | 16,435 |
<p>I' m asking this question out of sheer curiosity, my teacher was not able to explain it.
If I'm using logistic regression with categorical variables they are coded like {1,2,3}. I guess it wouldn't change my results if I used {4,5,6}. But what if linearity of coding wasn't kept? (say {4,10,99})? What I deal with is... | 10,042 |
<p>Since I had no answer to the second part of <a href="http://stats.stackexchange.com/questions/20414/balance-between-randomization-interspersion-and-even-initial-conditions-of-expe">this</a> question I would like to ask it again providing some more infos I gathered in the meantime.</p>
<p><strong>Context</strong><br... | 72,146 |
<p>I am currently in the process of implementing a model for soccer result prediction in JAGS. Actually, I have implemented several, but I have reached my most difficult challenge yet: A model described by Rue & Salvesen in their paper "Prediction and retrospective analysis of soccer matches in a league". Their mod... | 33,967 |
<p>Is it inappropriate to use odds ratio for groups that are subset of each other? For example, comparing GPA of female students to GPA of all the students. (This is just an example, not what I am really comparing)</p>
<p>This is a part of a larger project, and my main interest in doing this is to show that the result... | 33,968 |
<p>I am comparing the behavior of some implementations of Bayesian and frequentist approaches to parametric anomaly detection and currently trying to figure out the differences when the sample set is really small. The Bayesian case looks fairly simple - it is possible to estimate the probability of a given item being f... | 45,953 |
<p>I have a large set of location data from a social network and would like to conduct a mobility study with it. For each <em>object</em>, I have up to several thousand <em>locations</em> where this object posted from. I quickly summarized properties of objects, which are </p>
<ul>
<li>location count (simply the numbe... | 41,199 |
<p>I am a software engineer and I have been asked to look at some performance issues that we are having with some batch-jobs on a system I am working on.</p>
<p>The batch jobs generate data for different categories (A-Z), however the mix of categories varies depending on the time of day. The job is run 5 times a day. ... | 45,020 |
<p>Are there terms for measures of variation around the median? I know that we use "variance" for means of data but how can variance be defined for the median? Is there a similar statistic for median?</p> | 72,147 |
<p>I have been using the <code>Root Mean Squared Error</code> (RMSE) to measure the accuracy of values predicted using a model. I understand that the value returned is using the units of my measures (rather than a percentage). However, I would like to quote my values as a percentage. The approach that I have taken is t... | 72,148 |
<p>I have a longitudinal (panel) dataset for investment growth for 120 countries covering the time from 1960-2008. Essentially it's viewed as 120 time series. </p>
<p>What I am interested in is to group countries based on their shape of their growth curves over time. Thus whether they share similar Shape of their cur... | 45,023 |
<p>so I analyzed a nested design (split-plo, 2x4 factorial) with ANOVA and it indicated that there are differences in the levels of factor b.</p>
<p>I went on with t-tests comparing the means depending on factor b.</p>
<p>If the assumptions for t-tests are positive can I just compare 2 groups without considering the ... | 72,149 |
<p>The essence of LDA is word co-occurrence. I want to know why? and does word co-occurrence mean two words appear together in a certain document or just appear in the documents collection together? </p>
<p>Thank you all in advance.</p> | 72,150 |
<p>I work with data containing SNP genotypes for thousands of individuals. One of the task I had was to perform IBD between the individuals to find out the individual relatedness. I perform the IBD analysis with PLINK (<a href="http://pngu.mgh.harvard.edu/~purcell/plink/ibdibs.shtml" rel="nofollow">http://pngu.mgh.harv... | 72,151 |
<p>Consider the linear regression model</p>
<p>$${\bf y} = {\bf X}\beta + {\bf e},$$</p>
<p>where ${\bf y}$ is an $n\times 1$ vector, $\beta$ is a $p\times 1$ vector, ${\bf e}$ is an $n\times 1$ vector. Assume also that $e_j\stackrel{ind.}{\sim} N(0,\sigma)$.</p>
<p>What is the Jeffreys prior of the parameters $(\be... | 72,152 |
<p>I'm new in area of deep learning and for me first step was to read interesting articles from deeplearning.net site. In papers about deep learning, Hinton and others mostly talk about applying it to image problems. Can someone try to answer me can it be applied to problem of predicting time series values (financial, ... | 72,153 |
<p>I'm a new statistics student :) I have some questions about linear regression, i'm using R to do some tests.</p>
<p>I have two simple lists, like:</p>
<pre><code>> a <- c(1,2,3,4)
> b <- c(5,6,7,8)
</code></pre>
<p>then I do</p>
<pre><code>> model <- lm(a ~ b)
</code></pre>
<p>the result (coef... | 72,154 |
<p>Lots of people use a main tool like Excel or another spreadsheet, SPSS, Stata, or R for their statistics needs. They might turn to some specific package for very special needs, but a lot of things can be done with a simple spreadsheet or a general stats package or stats programming environment.</p>
<p>I've always l... | 49,320 |
<p>I am familiar with entropy as defined from information theory, which is simply</p>
<p>$ H(X) = \sum_{i=1}^{n} p(x_{i}) \log p(x_{i}) $,</p>
<p>for a discrete set of probabilities. In term of clustering, the entropy can be used to measure the quality of a clustering solution. It is defined as,</p>
<p>$ E(S_{r}) = ... | 72,155 |
<p>If one has an r value of 0.60, can one state that an increase in one variable is 60% likely to mean an increase in the other variable?</p> | 45,036 |
<p>I have what is probably a simple question, but it is baffling me right now, so I am hoping you can help me out.</p>
<p>I have a least squares regression model, with one independent variable and one dependent variable. The relationship is not significant. Now I add a second independent variable. Now the relationship... | 49,359 |
<p>How can I understand what the RBF Kernel in SVM does? I mean I understand the maths, but is there a way to get a feeling when this kernel will be useful?</p>
<p>Would results from kNN be related to SVM/RBF since the RBF contains vector distances?</p>
<p>Is there a way to get a feeling for the polynomial kernel? I ... | 72,156 |
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