question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am interested in stating that ___ % of the variance in Y is explained uniquely by $X_1$ and ___ % is explained uniquely by $X_2$. </p>
<ul>
<li>Is there some way to obtain this from a multiple regression model, or do I need to obtain adjusted $R^2$ values from a series of residual regressions (sensu Legendre &am... | 42,876 |
<p>I am reading a text, "Mathematical Statistics and Data Analysis" by John Rice. We are concerned with approximating the expected value and variance of the random variable $Y$. We are able to calculate the expected value and variance of the random variable $X$ and we know the relation $Y = g(X)$. So, it's possible to ... | 42,877 |
<p><a href="http://www.inf.fu-berlin.de/inst/ag-ki/adaboost4.pdf" rel="nofollow">A tutorial on AdaBoost</a> suggests that AdaBoost can be applied to a continuum of classifiers (at the bottom of the first page). Does it mean to simply discretize the classifiers, for example, which are parameterized by one or two real nu... | 32,189 |
<p>I'm looking to use n-fold cross validation for selecting meta-parameters for fitting a model to a dataset. However, dropping observations entirely from the learning-set while fitting the model to each of the folds may create problems for the model fitting.</p>
<p>I was wondering whether it would be valid to perform... | 32,190 |
<p>Looking for help to create a model for my data gathered from a reciprocal transplant experiment: I have 2 populations of fish (A and B) and 2 temperature regimes (warm and cold) that were crossed with each other (= 4 treatment groups- A:warm, A:cold, B:warm, B:cold). Each treatment group consists of two replicate... | 70,960 |
<p>I am reading <a href="http://www.cs.princeton.edu/~schapire/uncompress-papers.cgi/msri.ps" rel="nofollow">an overview of AdaBoost written by Schapire</a>, which calculates the upper bound of the training error in Eq. (5), section 3. In fact, it states that</p>
<p>$$\prod_{t}Z_t=\prod_{t}\left[2\sqrt{\epsilon_t(1-\e... | 70,961 |
<p>I have (what I will term, for lack of a better word) a random walk that has a particular property: it tends to be right of the origin some fraction <em>k</em> of the time and left 1-<em>k</em> of the time (and on the origin a negligible fraction). So although the probabilities of going up or down are close to 1/2, ... | 32,192 |
<p>I have been trying to find a method to analyse variance on Weibull and/or Gamma distributions but a Google search for</p>
<pre><code>anovar Weibull "gamma distribution"
</code></pre>
<p>yields nothing helpful. The data I have cannot be fitted to a normal distribution but fits a Weibull or Gamma distribution quit... | 70,962 |
<p>From the elements of statistical learning, it was claimed that
$$
\frac{1}{N}\sum_{i=1}^N ||h(x_i) ||^2 \sigma^2_\varepsilon= \frac{p}{N}\sigma^2_\varepsilon$$</p>
<p>where $h(x_i) = X(X^TX)^{-1}x_i$. Can someone show me how to prove this ? Thanks</p>
<p>This came from the image below</p>
<p><img src="http://i.s... | 70,963 |
<p>My data consists of 6 independent variables (continuous and categorical) and 8 dependent variables on likert scale (categorical). I want to use multinomial logistic regression to find out the relationship between dependent and independent variables. I reduced the 8 dependent variables by principal component analysi... | 5,977 |
<p>While reading <em>Discovering Statistics Using R</em> pp. 431-432, Dr. Field says that </p>
<blockquote>
<p>"There are a variety of tests designed to deal with these situations
[multiple comparison procedures with unequal group sizes &/or
different population variances], none of which are implemented in R... | 32,203 |
<p>I am often disappointed with PCA plots in the scientific literature. Typically PCA plots do not provide a breakdown of the variables and their weights, just something like PCA1 (70% variance explained), PCA2 (10% variance explained). How could one tell which variables are strongly loaded into a component?</p>
<p>Ar... | 70,964 |
<p>I've been training different observation sequences to obtain different HMMs corresponding to each observed data. Something intriguing is that I get one observation sequence represented by 1 state. What does that represent? Does this mean that it's somewhat repeating a process?</p> | 32,204 |
<p>The code for Kernel density estimation was given in a recent CrossValidated question by Julio Miguel Galvez entitled <a href="http://stats.stackexchange.com/questions/32565/kernel-density-estimation-with-an-epanechnikov-kernel-in-matlab">"Kernel density estimation with Epanechnikov kernel in Matlab"</a>, as follows.... | 70,965 |
<p>Is there a distribution that resembles the gaussian (normal) distribution, but such that it's probability density is nonzero only over a defined segment.</p>
<p>The question emerged when I tried to model the 'bullet spread' within a circle. Gaussian distribution works fine, but there is always a chance that the bul... | 42,897 |
<p>I am using a survey that contains several questions about various dimensions of performance for policy research institutes. Here, performance in the policy arena is unpacked into things like: </p>
<ul>
<li>quality of research, </li>
<li>overall ability to engage with policy stakeholders, </li>
<li>quality of recomm... | 70,966 |
<p>I am currently fitting a mixed effects model to some experimental data as follows:</p>
<pre><code>model <- lmer(Y ~ X + M + (1+X+M|Subject), data=mydata)
</code></pre>
<p>The meaning of the variables is not so important here, but $X$ is the predictor of interest while $M$ is a (suspected) mediating variable. Al... | 32,207 |
<p>I am measuring hormone changes in animals. I have three groups: Groups A, B, and C. In each group, blood was collected from the SAME individuals for hormone assay at 0, 15, 30, and 60 min. This was done in males and in females and I would like to keep in mind sex differences. </p>
<p>My question: do the changes we... | 32,208 |
<p>I have some code and output, and I would like to construct a model. I don't know how to construct a model using this output:</p>
<pre><code> require("splines")
x <- c(0.2, 0.23, 0.26, 0.29, 0.33, 0.46, 0.53 )
y <- c(0.211, 0.2026, 0.2034, 0.2167, 0.2177, 0.19225, 0.182)
fit <- lm(y ~ n... | 70,967 |
<p>I am modeling three events A, B, and C as Poisson processes with rates $\lambda_A$, $\lambda_B$, and $\lambda_C$ and I would like to calculate the likelihood of observing some data given my model.</p>
<p>A distinction that I have come across is the difference between an event happening at a specific time $t$, $P\le... | 70,968 |
<p>I <a href="http://stats.stackexchange.com/questions/66861/standard-errors-of-hyperbolic-distribution-estimates-using-delta-method">originally asked a question about the delta-method in the context of the hyperbolic distribution</a>. I got an answer there, which is useful, except that it says I should apply the <code... | 70,969 |
<p>I am trying to learn ttest and ANOVA for my project (i am a computer science student). I need to know that my subjects answers "effected" by the feedback they get from the first question.<br>
What should i use to show "sth did effect or not sth"?
ANOVA or ttest? </p>
<p>I am sorry if it sounds very stupid. Thanks... | 70,970 |
<p>I am new to using R. I am trying to figure out how to create a df from an existing df that excludes specific participants. For example I am looking to exclude Women over 40 with high bp. I have tried several times to use the subset () but I cannot find a way to exclude using multiple criteria. Please Help!</p> | 70,971 |
<p>Suppose I have 30 numbers that vary between 0 and 1.0 and which sum to 1.0. The mean is obviously 0.033. A client wants these scaled to lie between 0 and 1.0 but to have a mean of 0.5. By the way, I'll probably have to do this for any set of numbers (positive, negative, outside the range 0 - 1) so that they lie i... | 49,807 |
<p>I was wondering if it can be useful to use selected features from a wrapper algorithm (for example SVM-RFE) to train another classification model like k-NN or Linear regression.</p> | 70,972 |
<p>For example, can the results of the t test on y1 and y2 be interpreted in the usual way (i.e., like the results of the t test on x1 and x2)? If not, how should I go about testing whether or not y1 and y2 are drawn from the same population?</p>
<pre><code>#Error-free measurements follow a N(10,1)
#I don't know these... | 32,216 |
<p>This question is about using PCA as a dimension reduction method before feeding the data into a classifier. It's a common procedure to use PCA for a data set which contains a large number of features, and to only use the first several PCA-scores instead of the original features. <strong>My question is</strong>: Afte... | 42,905 |
<p>I am a newbie in visualizations. Nowadays, I regularly come across graph-based data that I need to visualize. However, different type of data requires different layouts. And as I do not have enough experience, I am not aware of the different graph layout algorithms.</p>
<p>I would like to have a list of graph layou... | 70,973 |
<p>The question seems simple but I just can't solve it. </p>
<p>I have twelve test scores and three are to be picked at random to determine the overall test grade. How can I calculate the probability of my final grade based on three randomly picked tests from the pool?</p>
<p>The test scores are as follows:</p>
<pre... | 32,221 |
<p>Is there any intuition why the ridge regression is strictly convex, while the LASSO is only convex? </p>
<p>Does it have to do with the "corners" of the L1 regularization? </p> | 211 |
<p>In neuroscience it is very common to measure the <a href="http://www.mathsisfun.com/games/reaction-time.html" rel="nofollow">reaction time</a> (RT) of subjects. Based on the RT conclusions can be made about personal working memory capability, IQ etc.</p>
<p>So I have such data, which came from some neuroscience exp... | 32,223 |
<p>I want to develop my skill set in the design and analysis of experiments in retail, where we conduct experiments (introduction of new package, new product, discount, etc.) in test stores while maintaining the status quo in selected control stores. After the end of the experiment, we conduct analysis of sales to see ... | 6,044 |
<p>I'm trying to predict weight change with an intervention from baseline variables. Literature search yields suggests several predictors. Univariate analyses with weight change as dependent and baseline variables give several more predictors. </p>
<p>I've entered both theoretical and GLM univariate predictors into a ... | 70,974 |
<p>I have a monthly time series (for 2009-2012 non-stationary, with seasonality). I can use ARIMA (or ETS) to obtain point and interval forecasts for each month of 2013, but I am interested in forecasting the total for the whole year, including prediction intervals. Is there an easy way in R to obtain interval forecast... | 42,908 |
<p>I have a data set (given below in my MATLAB code) y vs. x and my eventual goal is to fit it to a power law $y=ax^b$ to see what exponent $b$ I get. I did some non-linear least squares fitting and since NLLSF requires initial conditions I specified $b_0=10$ since that is what the expected value was. I noticed that af... | 70,975 |
<p>When conducting various statistical test why do we expect equality of variances/ homoscedasticity/sphericity etc.?</p> | 70,976 |
<p>I have a 10,000 dimensioned dataset where all attributes are numeric values. I would like to select the best e.g. 50 attributes out of 10,000 so that I can run regression algorithms on it.</p>
<p>I've tried Weka's PCA and CfsSubsetEval algorithms, however they were not capable of handling that much dimension (algor... | 70,977 |
<p>In a multiple partial linear regression setting, the book I'm reading has this sentence:</p>
<p>«As a consequence of the fact that residual are orthogonal to explanatory variables, the 'cleaned' variables $M_2Y$ and $M_2X_1$(which are the residuals) are uncorrelated with $X_2$»,</p>
<p>where $X=(X_1 X_2)$, with $X... | 70,978 |
<p>Suppose that I have two models, A and B (A nested in B), which are tailored to explain data from a single participant in an experiment. Example: I am modeling response times in a single participant. However, I have 20 participants. </p>
<p>I can fit A and B using MLE to each participant independently, and then obta... | 6,072 |
<p>When specifying a production function for regression, it is well known that one of the features of using a log-log model is that the estimated coefficients are the output elasticities w.r.t. their respective independent variables.</p>
<p>My question is does it then follow that if one regresses log(production) on lo... | 42,910 |
<p>I've been spending quite some time to figure out how I can get the best R squared value from randomization of some values in a linear regression equation. I have allele frequency data and 14 environmental gradient data. Allele frequency value is fixed, but 2~14 combinations of the 14 environmental variables are used... | 70,979 |
<p>I've recently came across topic known as PAC-Bayesain, but I cannot find a source to read about it. Any article that I came across are talking about its application in a specific area but there is no introduction to what it exactly is. </p> | 70,980 |
<p>The Wikipedia article on the <a href="https://en.wikipedia.org/wiki/Kolmogorov%E2%80%93Smirnov_test#Two-sample_Kolmogorov.E2.80.93Smirnov_test" rel="nofollow">two-sample Kolmogorov-Smirnov test</a> states that:</p>
<blockquote>
<p>The Kolmogorov–Smirnov test may also be used to test whether two
underlying one-d... | 32,236 |
<p>I would like to know if there is an analytical formula for the distribution of partial sums of standardized random variables. (Of course, if one standardizes a random variable, the sum of <em>all</em> the individual observations will be zero).</p>
<p>I have written a Python function that estimates quantiles by boot... | 32,238 |
<p>Let $Z_1$ and $Z_2$ be categorical random variables with $3$ and $2$ categories, respectively. Let $Y_1$ and $Y_2$ be $2$ continuous random variables. Define completely the GLOM (general location model) for the joint distribution of $Z=(Z_1,Z_2)^T$ and $Y=(Y_1,Y_2)^T$ </p>
<p>I couldn't solve this problem. Can anyo... | 70,981 |
<p>The following output is for a data set for monthly airport arrivals that have been log transformed, with first difference & seasonal difference. My interpretation from the SAS output is p=P=2 d=D=1 q=Q=1 How do you code the initial model estimation function by just interpreting the ACF PACF? diagnostics of the b... | 70,982 |
<p>In Time Series models’ transfer functions there is a decay parameter in the
formula (let’s call it b). In TSA package that decay parameter is not mentioned. When I used other software before (such as SAS) I used to determine b after analyzing ‘prewhitened series’. But
in TSA package in R there is no need to specify ... | 70,983 |
<p>Let's say that I have the data set $(X,Y)$ where $X$ is a p-dimensional variable and $Y$ is uni dimensional. I'm interested in the following model:</p>
<p>$$
\theta_y = E(Y|X) \\
\theta_{y^2} = E(Y^2|X) \\
\theta_{y^3} = E(Y^3|X) \\
\theta_{y^4} = E(Y^4|X)
$$</p>
<p>where the components of $X$ ente... | 70,984 |
<p>I am trying to implement a simple face recognition software using nonnegative matrix factorization. I have tried this on the ORL dataset which has 400 face images (40 people * 10 photographs). The input matrix consists of the column-reshaped-images ordered as V=[p1_1, p1_2, ..., p1_10, p2_1, p2_2, ...]. I expect to ... | 32,242 |
<p>Discrimination parameters in two-parameter model from <a href="http://en.wikipedia.org/wiki/Item_response_theory" rel="nofollow">IRT</a> are usually considered item parameters.</p>
<p>But I've come to doubt it.
Think about psychophysics; for example, detecting luminance.
I don't think anyone would say that discrim... | 32,243 |
<p>I have a question regarding SPSS. I have 7 constructs and each construct has 3 items/variables on a Likert scale. Example: </p>
<p>Construct 1 - Mobile Usage,
Item a - Liking,
Item b - Preferences,
Item c - Frequency</p>
<p>I want to estimate correlations between these constructs. My questions are:</p>
<ol>
<li>... | 70,985 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/1142/simple-algorithm-for-online-outlier-detection-of-a-generic-time-series">Simple algorithm for online outlier detection of a generic time series</a> </p>
</blockquote>
<p>I've got data on quantities so... | 49,496 |
<p>I have independent variables $X_i\in[0;1]$ and suppose they are uniformly distributed. If you want to minimize the total absolute deviation to a fixed number, how much can you gain from using the sample mean over the population median?</p>
<p>Therefore I am looking for</p>
<p>$f(n)=E_{\{x\}}\left(\sum^n|x_i-0.5|-\... | 70,986 |
<p>There was a general election where I live yesterday and the television network started calling out winners long before all ballots were opened.</p>
<p>They turned out right on all accounts, and I'm not really surprised they did. I know that statistics are absolutely viable. Still, I'm curious. Assuming:</p>
<ul>
<... | 70,987 |
<p>I am modelling logistic regressions in SPSS, the same model for different countries (well, with slight differences in the independent variables set due to collinearity diagnosis and stepwise results). The model seems to work fine for most countries. In two countries, I am having some issues with the same variable. T... | 70,988 |
<p>I have performed an experiment, where I have real and synthesised movie data. My participants were shown either a real movie, or a synthesised movie (of talking heads), in a random order, and had to guess whether the movie was real or synthesised.</p>
<p>I got a binomial test result of 0.58 (using MATLAB <code>bino... | 8,853 |
<p>Kindly help me with </p>
<p>1) The motivation for the three parameter gamma distribution and the resulting structure of its density.
2) The meaning of the location, scale and shape parameters here</p> | 70,989 |
<p>The research paper examines the reaction times on a task and incorrect answers are eliminated as errors. The study does not specify the analysis however report a result of ps > 0.1 . What statistical procedure may they have used? </p> | 70,990 |
<p>When I read "Elements of Statistical Learning", I met some difficulty in calculating the Bayes decision boundary of Figure 2.5. In the package <code>ElemStatLearn</code>, it already calculated the probability at each point and used contours to draw the boundary. Can any one tell me how to calculate the probability? ... | 32,250 |
<p>I would like to perform a robust correlation on a small sample (n<30).
What is the best estimation method to use?</p>
<p>I tried to get an overview over the plenty methods for robust statistics provided in R - I would be happy if anyone could give me some recommendations</p> | 70,991 |
<p>Let $\theta \in \Theta \subseteq \mathbb{R}^d$ be a parameter vector. </p>
<p>Let $Q: \Theta \rightarrow \mathbb{R}$ be a function mapping from the parameter space to the real numbers. </p>
<p>Let $Z_T$ be a a random vector representing a random sample, where $T$ is the sample size and $Z_T$ has support $\mathcal{... | 70,992 |
<p>The following very simple forecast has been very helpful to me in applying basic methods.. and I have read that Bayesian methods may be superior for small data forecasting but I have not seen any useful comparative examples. </p>
<p>Particularly ones that I could use to apply to the following problem.</p>
<p>There... | 37,798 |
<p>I am using panel data and I have to choose between fixed-effects and random-effects models.</p>
<p>I run the Hausman test, the H0 (i.e., the difference in the coefficients from the two models is not systematic) is rejected. Thus, I should use the fixed-effects.</p>
<p>I also run a second test, which is based on th... | 70,993 |
<p>I have an interpretation question.</p>
<p>I am running binary multilevel models on whether or not households have bank accounts. Apart from relevant economic, social and demographical household level variables I also include two contextual variables for the primary sampling units (PSU), which are either villages or... | 70,994 |
<p>I'm trying to create Random Forests in Matlab and there are more observations in some classes than there are in others. Do I need to specify this as a cost matrix or as a prior probability or will Matlab figure this out automatically and the fact the data is skewed won't matter.</p>
<p>Thanks </p> | 70,995 |
<p>I would like to perform a random walk on a J-dimensional simplex. However, since this is part of a metropolis-hastings algorithm application, my understanding is that the steps need to be drawn from a symmetric distribution (is this correct?)</p>
<p>I was wondering if there is a standard/established way to approach... | 70,996 |
<p>I'm trying to understand the results published in <a href="http://psych.nyu.edu/tropelab/publications/SagristanoTrope2002.pdf" rel="nofollow">Sagristano, Trope, and Liberman (2002)</a>. Specifically, I don't understand what analysis produced the result highlighted in the screenshot below. The basic design is a 2 (ti... | 70,997 |
<p>I have already read some books about both two structural equation models. It seems both SEMs are suitable to the situation with small observations and large variables.</p>
<p>I assume to use combine both two SEMs to create a more accurate model to analyse the data and structure.</p> | 70,998 |
<p>I am looking at levels of genes in a dataset and want to identify genes that do not vary much in terms of their expression level. While I can do this using the coefficient of correlation, calculating the covariance or by looking for number of genes within the botton x percent of genes using median absolute deviatio... | 70,999 |
<p>I am running a negative binomial regression in Stata and would like to know if I need to include the <code>vce(robust)</code> option in the model. I know the negative binomial regression is the best for the data I have. I've combed through so many sources and it seems like negative binomials already seem to take car... | 104 |
<p>One of my demographic variable is age. Age is measured as continues data not categorical. If I want to test differences between two groups to determine whether there is significant difference between them or not, shall I use independent t-test, or I have to covert it to categorical variable then calculate chi-square... | 6,178 |
<p>One common practice which increases the odds of obtaining spurious
results is to keep collecting observations after a preliminary
analyses are performed<sup>[1]</sup>. This occurs when the cutoff point for
collecting cases is set as the time when significance is reached.</p>
<p>Noting that, it seems that meta analy... | 71,000 |
<p>I have been reading up on multiple imputation, and I am interested in the between-imputation variance. However, not in the estimation of the parameters, but in the imputed values themselves.</p>
<p>(1) Suppose $x$ is vector with some missing values. I then perform multiple imputations an infinite amount of times ac... | 32,258 |
<p>I have used the <em>vglm()</em> function from the VGAM package to obtain a Weibull model for some data. I would like to plot the curve that this model is represented by. How do I do this?</p>
<p>Here's my input and output (I am comparing 'p_seen' to 'calculated_logmar', which exist in the dataframe 'dframe1'):</p>
... | 32,259 |
<p>I'm looking to analyse 400k replies to a Facebook-equivalent post to determine how many of them are written by bots, and how many of them are written by real people.</p>
<p>I don't have the resources to obtain all 400k replies, so I can only work with a sample (say, 4000 replies). I believe it's very likely that vi... | 32,263 |
<p>I am trying to decompose and forecast a weekly time series which is believed to be affected by moving holidays (e.g. Chinese New Year, which happens in different weeks of a year).
I would like create a regressor variable to reflect the holiday effect on the series.
Is it correct to use the regressor variable as xr... | 71,001 |
<p>I am performing a logistic regression on a rather big dataset (700k+ samples and 1k+ features). I suspect that a lot of these features will be highly correlated and multicollinearity can be an issue.</p>
<p>I believe that with elastic net regularisation is can perform feature selection and shrink the parameters of ... | 32,269 |
<p>Does anyone know the difference in calculation between these two AUC packages? They get different results when I add in positives with predicted value of 0 (simulating a prob model where many outputs will be zero e.g. randomForest). So I would like to know why there is the kink in the pROC results (red) and the AUC ... | 71,002 |
<p>it happened to me that in a logistic regression in R with <code>glm</code> the Fisher scoring iterations in the output are less than the iterations selected with the argument <code>control=glm.control(maxit=25)</code> in <code>glm</code> itself.</p>
<p>I see this as the effect of divergence in the iteratively rewei... | 71,003 |
<p>While searching for a job for data analyst I found out that many jobs where data analysis is widely used do not include "data" or "statistics" in position title, for example credit specialist, business analyst and so on. </p>
<p>What are suitable job positions for people who want to analyze data? Moreover, how they... | 32,270 |
<p><strong>What is be the optimal ratio of sample size to the number of parameters in the multiple regression model?</strong> </p>
<p>I am wondering as I would like to improve accuracy of prediction.
Some sources suggest a ratio of 3 to 1, whereas others suggest 10 to 1.
Any other suggestions?</p> | 71,004 |
<p>I am investigating the following problem: I have a large set of values, many of which are repeated. Measuring the number of distinct (or unique) values shows that their number grows much slower than the number of total values, so that with 2M values I get just ~260k distinct values, with 20M values it goes up to jus... | 6,349 |
<p>I have sparse overdefined system of linear equations.</p>
<p>For example I have n variables, m equations(m>n) and k equations from m are "bad" equations that represent outliers.</p>
<p>Is there any methods to solve this problem?</p>
<p>I already found techniques such as iterative reweighred least squares,LMeds,M-... | 71,005 |
<p>I would like to compare models selected with ridge, lasso and elastic net. Fig. below shows coefficients paths using all 3 methods: ridge (Fig A, alpha=0), lasso (Fig B; alpha=1) and elastic net (Fig C; alpha=0.5). The optimal solution depends on the selected value of lambda, which is chosen based on cross validatio... | 32,275 |
<p>I am confused and looking for advise. I have found myself in this same situation repeatedly in the last few months. </p>
<p>I want to know if covariate <em>X</em> is influential or important. However, I also hypothesize that covariate <em>K</em>, <em>L</em>, and <em>W</em> could be influential or are important.... | 71,006 |
<p>I am doing a one way ANOVA (per species) with custom contrasts.</p>
<pre><code> [,1] [,2] [,3] [,4]
0.5 -1 0 0 0
5 1 -1 0 0
12.5 0 1 -1 0
25 0 0 1 -1
50 0 0 0 1
</code></pre>
<p>where I compare intensity 0.5 against 5, 5 against 12.5 and so on. Th... | 37,434 |
<p>I perform ridge regression for classification. To find regularization parameter I do K-fold cross-validation with classification accuracy as a measure.
This gives me some $\lambda$, which I then use in training of a final model on the whole available training data. The problem is that when I take 10*$\lambda$ my te... | 71,007 |
<p>10 kids had access to 4 computers, each with a different game (a-d). The test was 5 min. </p>
<pre><code>kid 1 played game a for 238 sec
kid 2 played game a for 263 sec
kid 3 played game b for 280 sec
kid 4 played game a for 245 sec
kid 5 played game a for 220 sec, game b for 25 sec, and game d for 78 sec
kid 6 pl... | 4,940 |
<p>Let $\textbf{X}$ be an $n \times p$ matrix with the rows containing observations and the columns containing features. Also assume that the features are centered at $0$. Let $C_k\subset \{1, \dots n \}$ contain the indices of the observations that belong to class $k$. Why is an estimate of the within-class covarianc... | 42,962 |
<p>Suppose you have one variable, $x$, with 8 data points, with a sample mean of 60%, and a sample standard deviation of 7%, and let’s also assume you know the sample comes from a lognormal distribution (or from a distribution with a heavier tail than lognormal).</p>
<p>A sample with mean = 60%, SD = 7%, could be prod... | 71,008 |
<p>I have been working on a research paper related to source code authorship attribution. In order to measure the performance of the technique, described in my paper, I need several data sets.</p>
<p>Following papers described similar systems and tested those systems using several datasets. Unfortunately these dataset... | 71,009 |
<p>Let's say $X$ has a log-normal distribution and there is one real positive number $c$. then is it right to say that $(X -c)$ also has some log-normal distribution? My feeling is that, it can't be, because $(X - c)$ may take negative value whereas a log-normal distribution is only defined on the positive domain. Can ... | 71,010 |
<p>I'm comparing a sample and checking whether it distributes as some, discrete, distribution. However, I'm not enterily sure that Kolmogorov-Smirnov applies. <a href="http://en.wikipedia.org/wiki/Kolmogorov%E2%80%93Smirnov_test">Wikipedia</a> seems to imply it does not. If it does not, how can I test the sample's dis... | 48,191 |
<p>What if any is the connection between SVD (the one you learn about in your linear algebra course) and SVD++ (the one from the Netflix prize)? I know they both want to find latent factor spaces. But that seems to be it. Am I missing anything?</p> | 71,011 |
<p>The wiki article on <a href="http://en.wikipedia.org/wiki/Credible_interval" rel="nofollow">credible intervals</a> has the following statement:</p>
<blockquote>
<p>credible intervals and confidence intervals treat <a href="http://en.wikipedia.org/wiki/Nuisance_parameter" rel="nofollow">nuisance parameters</a> in ... | 71,012 |
<p>Is it okay to perform a Kruskal-Wallis on four unequal samples? Further to this, is there a subsequent pair-wise post-hoc suitable for two unequal sample sizes?</p> | 71,013 |
<p>I need to have one understanding on statistical hypothesis testing. In a typical hypothesis test, we have 2 opposite hypotheses; namely Null and Alternative. Here my textbook says that "those 2 hypotheses are not symmetrical in the sense that if we swap the hypotheses then the result will alter".</p>
<p>Here I am u... | 71,014 |
<p>I've created my own slightly enhanced version of the termplot that I use in this example, you can find it <a href="http://pastebin.com/hBmStX4Y" rel="nofollow">here</a>. I've previously posted on <a href="http://stackoverflow.com/questions/9056934/problems-with-standard-errors-in-rms-package-for-an-adapted-version-o... | 42,982 |
<p>Before I ask my question, let me give you a bit of background about what I know about statistics so that you have a better sense of the types of resources that I'm looking for.</p>
<p>I'm a graduate student in psychology, and as such, I use statistics almost every day. By now I'm familiar with a pretty broad array... | 49,735 |
<p>Let $A[n\times m]$ represents the term-document matrix, where, $n$ is the number of terms and $m$ is the number of documents. This matrix can be composed into 3 matrices (SVD decomposition) such as,
$A = U\times W \times V^T$ </p>
<p>Its truncated version can be written as:
$A_k = U_k\times... | 71,015 |
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