question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I was reading about item-item collaborative filtering at:
<a href="http://guidetodatamining.com/guide/ch3/DataMining-ch3.pdf" rel="nofollow">http://guidetodatamining.com/guide/ch3/DataMining-ch3.pdf</a></p>
<p>But I did't find an implementation in R of this algorithm.
Is there one?</p> | g61684 | [
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<p>I am trying to find out if change in marital status have effect on person's health. I am using 2 data points panel data. </p>
<p><img src="http://i.stack.imgur.com/SLM2H.jpg" alt="Random and Fixed Effects"></p>
<p>My question is, how to interpret fixed coefficients if independent variable is categorical? Does coef... | g61685 | [
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<p>I'd like to choose a statistical solution for the next years which can manage the major forms of text mining analysis, like mood detection.</p>
<p>Is there a solution which stands out from others (R, SAS, SPSS,...) ?</p> | g61686 | [
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<p>I have collected player match history statistics like runs, shoots, passes and such. I would like to come up similar attribute values (psychical, mental, technical) to Football Manager game or footballdatabase.eu . What would you suggest to come up such a statistical formulation for each attribute based on known num... | g61687 | [
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<p>Which Transformation should i apply for the data which having 0's and large values?
min value is - 0 and
max value is - 2254</p>
<p>here we should not delete any cases from the data.</p> | g32571 | [
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<p>I have studied algorithms for clustering data (unsupervised learning): EM, and k-means.
I keep reading the following : </p>
<blockquote>
<p>k-means is a variant of EM, with the assumptions that clusters are
spherical.</p>
</blockquote>
<p>Can somebody explain the above sentence? I do not understand what spher... | g61688 | [
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<p>My model is working ok (the AUC is 0.7) but the importances from a <code>randomForest</code> run for my binary classification problem differ depending on how I retrieve them. Is this normal? They seem to be scaled up when I call <code>importance(rf)</code> (by order 10<sup>5</sup>). More importantly, the first three... | g18388 | [
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<p>I am running a model where one of the explanatory variables is truncated. In particular, the variable measures the duration of unemployment (retrospectively) in months and it is truncated at 2 years, which happens for around 10% of the sample. In my model I want to treat the variable as continuous (as I already have... | g61689 | [
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<p>I'm trying to train single layer perceptron. I don't understand one thing. How to calculate output for vector input x?</p>
<p>For example let say we have this data to use for training:</p>
<pre><code>L1 = [1.5 2.4; -0.3 3; 2 3; 2 2.5];
L2 = [2.5 1.4; -1.3 2; 3 3.1; 1.2 2.5];
</code></pre>
<p>weight init, step:</p... | g61690 | [
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<p>I'm evaluating a classifier to detect objects.</p>
<p>For example:<br>
I have a set1 with 50 pictures with the object to detect.<br>
And set2 with 100 pictures without the object.</p>
<p>I determine the true positves (0 in set2), true negatives (0 in set1), false negatives and false positives for those sets.</p>
... | g18390 | [
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<p>So let's say I have two different sets of features A and B. I'm trying to determine which set of features is the best. I'm using leave-one-out cross validation as the final metric as my data set is small. I'm trying to figure out my experimental setup and I'm deciding between a few ways:</p>
<p>1) Give feature set ... | g18391 | [
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<p>Let $X$ and $Y$ be two continuous random variables. Suppose that:</p>
<ol>
<li>$X$ has normal pdf with mean mu_1 and variance $\sigma_1^2$</li>
<li>$Y|X$ has normal pdf with mean $mu_2=(a+b*X)$ and variance $\sigma_2^2$; where a and b are two constants from linear regression</li>
<li>$f(Y)=\int f(Y|X)f(X) dx$; wh... | g18392 | [
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<p>I have a panel including two years and I want to compare urban and rural wages:</p>
<p>$\log \text{wage}_{it} =\beta_0 +\beta_1\text{urban}_{it} +\beta_2\text{educ}_{it}+\beta_3\text{exper}_{it}+ \beta_4\text{exper}_{it}^2+\delta_2+\nu_it$ </p>
<p>urban is a dummy as well as $\delta_2$ for the second year</p>
... | g61691 | [
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<p>I am currently running a study with two groups (controll and current psy. disorder). All participants have three conversations, are videotaped and watch the videos of their interactions afterwards, two times. While watching the video, I assess my dependent variable. The tree conversations are the three levels of the... | g18393 | [
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<p>I need advice about how to carry out an ANOVA. I studied some theory of ANOVA, but apparently it is not enough.</p>
<p>Basically I collected around 300 reaction times for 12 subjects in my experiment. For each subject I had 2 conditions. The first has 3 levels, the second has 5 levels. Each subject went through all... | g18394 | [
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<p>What are the differences between those Population and Standard Deviation and what are their fomulas? I was told that they are different formulas and which situation do you use population or sample?</p>
<p>If a user gives 10 random numbers, would I be using population or sample?</p> | g61692 | [
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<p>I'm getting very different output when i perform a multinomial ordinal model depending on wether I scale or not my data first. Anyone could tell me why?</p>
<p>Here are the results with raw data:</p>
<pre><code> polr(formula = result ~ 1 + Speed + rsvl + rsvl:Speed + tailcontrst:Reltailsize +
strategy:rsvl, data... | g28262 | [
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<p>I have a setup where the joint posterior is written as:</p>
<p>$$
P(w, \lambda, \phi \vert y) = P(\phi) \times P(w \vert \lambda) \times P(\lambda) \times \prod_{i=1}^{N}P(y_i \vert w_i, \phi, \lambda)
$$</p>
<p>Now $\phi$ and $\lambda$ are modelled as Gamma distributions and the likelihood and prior on $w$ is nor... | g3813 | [
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<p>I want to calculate a better bandwidh for my kernel density estimator, which is an Epanechnikov. I use Silverman's formula which involves the standard deviation of the sample, the sample size and a constant, but I'm getting a very smooth curve in most cases and I would prefer if it were more balanced. Thank you for ... | g61693 | [
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<p>I have the number of monthly flights, and the number of the active cabin crew in monthly basis, and the number of crew who were absence (sick leave or so) in monthly bases as well. How do I get an index or indicator about the absence rate? I want to know are things are improving or not by using all three parameters ... | g61694 | [
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<p>Basically, I'm conducting research based on two types of data: Noise levels and the temperature of a room. I've recoded data for 2 days.. I am using the spearman's correlation methods to determine whether or not there is a correlation between temperature changes and the level of noise.. </p>
<p>The problem is that ... | g61695 | [
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<p>I'm analyzing data from a political opinion survey. The survey is administered once a year to roughly 1000 citizens from 18 different European countries.</p>
<p>In a first step, I am interested in gauging the relationship between various individual-level variables for all respondents over the past four years. My de... | g61696 | [
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<p>If you were attempting to forecast the outcome of a general knowledge quiz competition with predictors such as age, education levels, IQ etc there seems to be several obstacles to using say conditional logistic regression, or other classifications into Y=1 (100% winner) or Y=0 100% loser, even if you came second in ... | g61697 | [
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<p>I'm trying to use a Bernoulli mixture model to classify MNIST images, and I'm running into pathological cases which screw up my calculations.</p>
<p>The pdf of a multidimensional (let's say N dimensions) Bernoulli distribution is as such:
$P(x|\mu) = \prod\limits_{i=0}^{N}\mu_{i}^{x_i}(1 - \mu_{i})^{(1 - x_i)}$</p>... | g32741 | [
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<p>I would like to generalize Paul Teetor's <a href="http://quanttrader.info/public/betterHedgeRatios.pdf" rel="nofollow"><strong>A Better Hedge Ratio</strong></a>, which uses prcomp() to determine a TLS ratio between two variables. I am hoping to extend this to multiple variables, but am having trouble finding accurat... | g18405 | [
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<p>I use the following code to train an svm classifier:</p>
<pre><code>clf = svm.SVC(kernel='linear')
clf.fit(train_mat, train_labels)
</code></pre>
<p>that fit the data and save the info in the <code>clf</code> object.
Now I know how theoretically the <code>w</code> vector is constructed. It is a sum over all suppo... | g61698 | [
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<p>I am working on a 2-class classification problem and using LIBSVM. I am facing this following problem with cross validation (CV). Any help is highly appreciated. </p>
<p>When I perform a 10 fold CV with -v 10 option, I get an accuracy of 90%. But when I do a training and testing on the same data with 90-10 split, t... | g61699 | [
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<p>I had run the mixed model for repeated mesurement using SAS proc mixed, I got the model(s) already for my dependent variable. However, proc mixed doesn't provide R^2. Is there any cross validation methods that can apply to my data set. Or just simply tell people that I used proc mixed and no R^2 (which i think that ... | g31039 | [
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<p>The misclassfication rate in decision trees is defined as $$1-\max_{j} p_{j}$$</p>
<p>Suppose we want to classify people into republicans and democrats. In the training data, $\hat{p}_1 = 0.7$ (probability of being republican) and $\hat{p}_2 = 0.3$ (probability of being a democrat). If we split on $\text{age} \leq ... | g61700 | [
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<p>I am testing the statistical significance of 60 strong correlated quantitative variables in 2 groups, with small sample size, non normality and presence of outliers.
I have implemented a permutation test based in the t-test statistic for deal correctly the correlation structure of the variables; but I think this per... | g9908 | [
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<p>I use simple regressions. My independent variable is a count data (# of a drug used per year), and it has too many zeroes. Depending upon a dependent variable, for some simple regressions, I have 13 observations, and there are only 3 non-zero values out of 13. For other simple regressions, I have 150 observations an... | g61701 | [
0.012270649895071983,
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0.009420742280781269... |
<p>I would like to investigate interactions between my explanatory variables prior to building a statsitical model. </p>
<p>Apparently it is possible to do it in R using a regression tree (library: tree). This method is based on binary recursive partitioning. The algorithm predicts a response variable by partitioning ... | g61702 | [
0.044699665158987045,
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<p>I am not very expirienced in the field of machine learning. </p>
<p>For now I model some binary classifier using k-NN. I experimented a bit with different values of k. In some cases the best one was with <code>k=1</code>. I know that there is no majority voting, and my decision is made on single neighbour, what see... | g18417 | [
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<p>I've been having a little trouble with some data I've been trying to analyse. I've got 2 populations of protein crystals, one subjected to a humidity stream and one not, with a view to see if there are any effects on data quality. For most of my tests there hasn't been any problem but for one set of populations the ... | g49294 | [
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<p><em>Disclaimer: I don't have sufficient statistics' background or vocabulary for this question, but I did my best to do a preliminary search both within the forum and the broader interwebs</em></p>
<p>Is there a way for one to determine a formula or its simplified approximation from a set of results?</p>
<p>My sol... | g48288 | [
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0.0071... |
<p>Could anyone give me some information on who invented profile maximum likelihood estimation or who first use profile maximum likelihood estimation and the short history of profile maximum likelihood estimation? I would like to know about any paper on this.</p> | g61703 | [
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<p>Thinking about a normal linear regression, penalized by the L1 norm. That is the lasso, is there any literature on median ridge regression?. That is the residuals are calculated from an L1 norm instead of a squared norm. Then the penalization is by the square norm. My intuition tells me this will bring about variabl... | g61704 | [
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<p>I have two distributions where only the 5-number summary (minimum, 1st quartile, median, 3rd quartile, maximum) and sample size are known. Cntrary to the question <a href="http://stats.stackexchange.com/questions/18408/two-samples-of-the-same-distribution">here</a>, not all data points are available.</p>
<p>Is the... | g61705 | [
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<p>I have to regress family income (<code>faminc</code>; in dollars) onto <strong>husband's educational attainment</strong> (<code>he</code>; in years), <strong>wife's educational attainment</strong> (<code>we</code>; in years), and <strong>number of children less than 6 years old in household</strong> (<code>kl6</code... | g61706 | [
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... |
<p>We have just finished an experiment, where we had samples distributed into 6 groups and each group receiving a different treatment. Each group had 5 samples, with 20 replicate measurements taken per sample (they do not represent timepont difference, but mainly replicates). The data looks something like this</p>
<p>... | g61707 | [
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0.037133753299713135,
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0.0... |
<p>Suppose that, in a study of 15 subjects, the response variable (res) is modeled with two explanatory variables, one (level) is categorical with 5 levels and the other (response time: RT) is continuous. With lmer in the lme4 package of R, I have:</p>
<pre><code>fm1 <- lmer(res ~ level * RT + (level-1 | subject),... | g18427 | [
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... |
<p>I have a randomized experimental dataset with six treatments with each approx. N=60. The outcome is a time-series, namely deforestation in a land-use simulation game over 40 rounds.</p>
<p>I managed to show that the impact of the treatments on the state of the land (i.e. number of cummulative cells deforested) is h... | g61708 | [
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0... |
<p>Suppose that I have a population, each represented by a bit $b_i$ for $i \in \{1,\ldots, n\}$. I would like to compute an estimate $\hat{B}$ of the parameter $B = \sum_{i=1}^nb_i$ so that with high probability, the error $|\hat{B}-B| \leq k$ for some fixed $k$. However, I have to pay a cost $c_i$ to sample bit $b_i$... | g61709 | [
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... |
<p>I am trying to get a deeper understanding of the various types of Bayesian networks. </p>
<p>Most of the literature/lectures I've come across use discrete random variables exclusively and only mention continuous random variables in passing. </p>
<p>It seems if you want to mix discrete and continuous variables in ... | g48307 | [
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0.03276190161705017,
-0.0... |
<p>What is the difference between soft and hard expectation maximization?</p>
<p>EDIT: ok, i've found out this paper: <a href="http://ttic.uchicago.edu/~dmcallester/ttic101-07/lectures/em/em.pdf" rel="nofollow">http://ttic.uchicago.edu/~dmcallester/ttic101-07/lectures/em/em.pdf</a>
that explain quite well the situatio... | g48308 | [
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0.... |
<p>I have a response variable which is right skewed.
There are lot of low values, less than 10 and then extremely large outliers.
I want to create a model which can predict the max values that the variable can attain.
Which techniques can I use to predict the max value</p> | g61710 | [
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0.03703664243221283... |
<p>What are the differences between generative and discriminant models (in the context of Bayesian learning and inference)?</p>
<p>and what it is concerned with prediction, decision theory or unsupervised learning?</p> | g61711 | [
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<p>What are the most important statisticians, and what is it that made them famous?<br>
(Reply just one scientist per answer please.)</p> | g61712 | [
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<p>I am trying to state a prior distribution for a Bayesian meta-analysis.</p>
<p>I have the following information about a random variable: </p>
<ol>
<li>Two observations: 3.0, 3.6</li>
<li>a scientist who studies the variable has told me that $P(X<2)=P(X>8)=0$, and that values as high as 6 have nonzero probabi... | g18444 | [
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... |
<p>I have a question regarding the sign test when the individual measurements may be correlated. Let me start off with some background. Suppose we have 4 Organisms (a,b,c,d),and we make measurements in two separate ways, say A and B. Our data may look as follows</p>
<p>a = 3 for measurement A and 1 for measurement B<b... | g61713 | [
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0... |
<p>I asked this question on mathoverflow yesterday and got a suggestion to try it here. I apologize if this is an easy question, but I can't seem to find an answer anywhere.</p>
<p>I'm trying to duplicate a macroeconomic paper that uses MCMC analysis to derive time series and parameter values. For the variance of a wh... | g48328 | [
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<p>I am working with a very sparse problem with a large number of categories per feature and I am currently looking for existing machine learning regression algorithm implementations which can either take a large number of categories per feature as input (say 10^4 categories), or can operate on sparse input design matr... | g29382 | [
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0.05075059086084366,... |
<p>I'm working through some problems on deriving U-statistics, and I am unsure about determining the number of samples (random variables?) that are needed for the kernel of a given U-stat. For example:</p>
<p>Let $X_i$ be $iid$ with unknown Lesbegue PDF. Let $\mu = EX_1$, $\sigma^2 = VAR(X_1)$ and $EX^4 < \infty$. ... | g61714 | [
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0.034221261739730835,
0.012531070969998837,
0.04338305816054344,
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0.0... |
<p>I did a regression and found that my residuals pointed out that my data is heteroscedastic.
I applied the Box-Cox transformation and my new model looks as follows, </p>
<pre><code>y^(1/5) = b0 + b1x1 + b2x2
</code></pre>
<p>with my lambda = 1/5 and I found my b0, b1 and b2 values. This transformed model does not ... | g3821 | [
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<p>I know my question is kind of general and wide but I wrote it to narrow it down by your idea!</p>
<p>Lets say we have an incomplete dictionary of very old language and we want to complete it! There are a lot of documents contain sentences.</p>
<p>At the first we fill the dictionary by the closest language to this ... | g61715 | [
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<p>How to compute the density function of the <em>k</em>-th order statistic of a sample of $X_1, X_2, ..., X_n$ random variables distributed independently but not identically (i.e., $X_i \sim F_i$ with $F_i\neq F_j$)?
What would be the explicit solution if each $F_i$ is uniform on $[m_i,1]$ with $0<m_i<m_{i+1}&l... | g61716 | [
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0.03336282074451446... |
<p>I have a relatively large sample (400 pat) with two continuous variables (almost) normally distributed.
May I use ANOVA to correlate the ratio between those 2 variables with a third nominal variable?
Many thanks</p> | g3824 | [
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<p>Why doesn't the biglars.fit function work when maxStages is specified? I've tried multiple values and multiple ways of casting $y$ but it doesn't work.</p>
<pre><code> x <- as.ff(matrix(rnorm(100*20),ncol=20))
y <- as.ff(matrix(rnorm(100)))
fit <- biglars.fit(x,y,maxStages=5)
Error in `[<-`(`*tmp*`,... | g61717 | [
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0.01265520229935646,
0.03667234629392624,
... |
<p>My data is as follows: in a routing node (check <a href="http://dl.dropbox.com/u/5363697/Mdl/Note%20Jul%2030%2C%202012.pdf" rel="nofollow">figure</a> ), I can see the entry and exit gate of each packet, so I have pairs like this: </p>
<pre><code>(1,5) (2,5) (1,6)...
</code></pre>
<p>where the first number of each ... | g61718 | [
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0.037713173776865005,
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0.... |
<p>According to my modest understanding, the cox model is all about estimating hazard ratios, relative measures of risk.</p>
<p>However, it is possible (in R using e.g. the packages pec or peperr) to estimate absolute risks by a cox model.</p>
<p>How is this done mathematically?</p> | g18456 | [
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<p>Suppose we have $n$ samples, with mean $\mu$.</p>
<p>Calculate the average absolute distance from $\mu$, i.e.,
$$
y = \frac{1}{n} \sum_{i=1}^n |X_i - \mu| \>.
$$</p>
<p>Then, take as an estimate of the standard deviation
$$
\tilde \sigma = \frac{1}{\sqrt{2\pi (1-1/n)}} y \>.
$$</p> | g61719 | [
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0.0139381792396307,
0.029206683859229088,
0.04154790937900543,
0.014232873916625977,
0... |
<p>I have some questions about unique variance and hope some of you can help.</p>
<p>For instance, let say I have 3 predictors and 1 dependent variable (DV).</p>
<p>I ran a regression analysis with a sequence of 3 regression models using:</p>
<ol>
<li>Predictor A</li>
<li>Predictor A + Predictor B</li>
<li>Predictor... | g18457 | [
0.018142525106668472,
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0.005748298950493336,
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0.059777457267045975,
0.002338514430448413,
0.013006730005145073,
0.05455588549375534,
0.0048126960173249245,
-0.052404988557100296,
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0.016605626791715622,
0.011257318779826164,
-0.... |
<p>I am writing a report to show my results where, if there are more than 3 consecutive English character in a term, that term is noise. For example, "wooooh", "Noooo", etc. I have collected 100 sample and manually evaluated them. May I know what test should I perform to verify my hypothesis? Is it something like ANOVA... | g61720 | [
0.04813931882381439,
0.015094060450792313,
0.005823676008731127,
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0.02546933852136135,
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0.06035491079092026,
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0.07269... |
<p>As shown in the Google Web Optimizer example I would like to calculate the chance of beating baseline (original) - I tried around but couldn't figure out how they do it. I think the +- next to the conversion rate is the standard error but my standard error is off as well. </p>
<p>Anyone an idea how Google calculate... | g44019 | [
-0.0010506632970646024,
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0.05028432607650757,
0.03960336372256279,
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0.08803689479827881,
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<p>Is the any nice bound on tail distribution of a finite sum of i.i.d weibull random variables? </p> | g18459 | [
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0.0033046614844352007,
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<p>I am currently attempting to work my way through Gelman and Hill's textbook on regression. I am stuck at the very first exercise. The text reads as follows:</p>
<ol>
<li>A test is graded from 0 to 50, with an average score of 35 and a standard deviation of 10. For comparison to other tests, it would be convenient t... | g61721 | [
0.00997980497777462,
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0.013012788258492947,
0.05227518081665039,
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<p>I have a relatively novice question which I have been attempting to peruse the literature for the past hour to address without much success.</p>
<p>I am attempting to test a product concept in a survey for adoption, and would like to have a question with a 5-point rating scale to test the <strong>likelihood to use<... | g18460 | [
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0.005048631224781275,
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0.033618927001953125,
0.04155848175287247,
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0.0231741052120924,
... |
<p>I have this <a href="https://github.com/aronlindberg/VOSS-Sequencing-Toolkit/blob/master/rubinius_rubinius_sequencing/input.csv" rel="nofollow">data</a>:</p>
<pre><code>created_at actor_attributes_email type
3/11/12 7:28 jeremy@asynk.ch Event
3/11/12 7:28 jeremy@asynk.ch PushEvent
3/11/1... | g48349 | [
0.001158932689577341,
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0.009055533446371555,
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0.0637606680393219,
0.030816687270998955,
0.005874313414096832,
-0.0637437254190445,
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0.036425601691007614,
0.067391537129879,
0.060666... |
<p>Suppose I have census (count) data for a migratory species passing through a set of locations, at irregular intervals -- $n(i,t)$ is how many individuals were present at location $i$ on day $t$ for an irregularly spaced, and different, set of dates $t_1$, ... , $t_n$, for each location $i$. For the first part of ea... | g18461 | [
0.029895229265093803,
0.004337811376899481,
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0.02333124354481697,
0.014745821245014668,
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0.0393969751894474,
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0.0861876830458641,
... |
<p>I am trying to fit an ARIMA model for a certain financial time series. I've used EViews for modeling, and have decided to fit a so-called reduced-form MA(3) model, where only the third lag is statistically significant.</p>
<p>Unfortunately, I have not been a to figure out how to do this in R. All I can find is how ... | g61722 | [
0.06385728716850281,
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0.011769019067287445,
0.027604395523667336,
0.05882478505373001,
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0.02235628291964531,
0.013925598934292793,
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0.03337225690484047,
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<p>From my understanding baseline hazard is never estimated in Cox PH models and hazard ratio is all that we get from them. But sometimes we are more interested in comparing survival functions than just interpreting the hazard ratio. And, I think there exist some approximation methods for estimating survival function f... | g61723 | [
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0.01826024055480957,
0.014295859262347221,
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0.09372323006391525,
0.01... |
<p>I have a linear model for an experiment using repeated measures. Thus far I've used lme in R to test the model. For this model the the latest lag is 6. The ACFs are:</p>
<pre><code>Lag: 1 2 3 4 5 6
ACF: 0.01076084, 0.04204100, -0.11440165, 0.01422727, -0.067612... | g61724 | [
0.02163902297616005,
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0.032779939472675323,
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0.08298220485448837,
0.010690313763916492,
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-0.03587115928530693,
0.007860303856432438,
0.01527990773320198,
0.02607891894876957,
-0.06... |
<p>I’m trying to correlate data between an accelerometer and a pedometer (step counts). These are worn simultaneously by 20 people for 7 days. If the two devices give me 1 datum per day at the end of the week, I will have two sets (pedometer and accelerometer) of 7 days (dependent data) by 20 people (independent data) ... | g61725 | [
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0.01572079211473465,
... |
<p>Assume a linear regression with metric predictors: y ~ x1 + x2 + x3</p>
<p>Assume all x are significant predictors. </p>
<p>Now I want to find out if predictors differ from each other, that is, if one predictor is a stronger predictor of y than the others, and on top of it, if it is <em>significantly</em> stronger... | g18463 | [
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0.014464456588029861,
0.011317511089146137,
0.04168953001499176,
-0.039... |
<p>I have two finite sequences of numbers derived from one or more unknown processes. What is the most powerful test (in sense that it is least affected by finite length L) to find out whether two sequences were generated by the same process or not?</p> | g18464 | [
0.055647123605012894,
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0.021105891093611717,
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0... |
<p>I get output like this ..</p>
<pre><code>=== Stratified cross-validation ===
=== Summary ===
Correctly Classified Instances 85 53.125 %
Incorrectly Classified Instances 75 46.875 %
Kappa statistic 0.0625
Mean absolute error ... | g18465 | [
0.05179470404982567,
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0.053430281579494476,
0.05409861356019974,
0.011388889513909817,
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0.03637806698679924,
0.04905933514237404,
0.026076458394527435,
0.05404370650649071,
0.016... |
<p>I will try to describe the problem at hand as general as possible. I am modeling observations as a <a href="http://en.wikipedia.org/wiki/Categorical_distribution" rel="nofollow">categorical distribution</a> with a parameter probability vector theta.</p>
<p>Then, I assume the parameter vector theta follows a <a hre... | g48362 | [
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0.0015219489578157663,
0.032364994287490845,
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-0.020754793658852577,
0.010729603469371796,
-0.04276992380619049,
0.03386576101183891,
0.... |
<p>Can someone please explain why do we use Log Linear Models in very lay-man terms? I come from Engineering background, and this is really turning out to be a difficult subject for me, statistics that is. I will be grateful for a response.</p> | g61726 | [
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<p>A new instructional strategy has been proposed to teach Freshman English. Students will be randomly assigned to two groups. One group will receive the treatment, or the new instructional strategy. The final test grade will serve as the student performance measure.
What would you propose as the research design? Why?
... | g18467 | [
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0.0003414575185161084,
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<p>How can I sample from a mixture distribution, and in particular a mixture of Normal distributions in <code>R</code>? For example, if I wanted to sample from: </p>
<p>$$
0.3\!\times\mathcal{N}(0,1)\; + \;0.5\!\times\mathcal{N}(10,1)\; + \;0.2\!\times\mathcal{N}(3,.1)
$$</p>
<p>how could I do that?</p> | g18469 | [
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<p>From a mathematical standpoint Bayes' Theorem makes perfect sense to me (i.e., deriving and proving), but what I do not know is whether or not there is a nice geometric or graphical argument that can be shown to explain Bayes' Theorem. I tried Googling around for an answer to this and surprisingly I was not able to... | g18470 | [
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0.013415791094303131,
0.033356357365846634,
0.04410415515303612,
0.027872586622834206,
0.0... |
<p>This question might probably also fit into Academia.SX. I'm writing my first paper in life sciences and I'm very often seeing asterisks as indicators for statistical significance (<em>*</em>).</p>
<p>I'm wondering if there's a convention on which symbol, and how many of them are to be used to indicate what the sign... | g61727 | [
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0.... |
<p>I know </p>
<ul>
<li>the average of a group that consists of two subgroups. </li>
<li>the number in the two subgroups </li>
<li>the total </li>
<li>the average of one of the subgroups. </li>
</ul>
<p>How can I work out the average of the other subgroup? </p>
<p>Basically, overall average of group of say 200 is 6... | g61728 | [
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0.004901582840830088,
0.0340600311756134,
0.03192473202943802,
0.008385831490159035,
-0.00... |
<p>I'm trying to run a <code>cforest</code> model in R with continuous and categorical variables. When I tried this in <code>randomForest</code>, the explained variation was ok, but there was a large bias towards continuous variables. Therefore I switched to <code>cforest</code>, using the codes provided by Strobl et a... | g18474 | [
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0... |
<p>I want to compare two samples with a Kolmogorov-Smirnov test. Wikipedia states the null hypothesis is rejected at $\alpha$ if:</p>
<p>$\sqrt( \frac{nn'}{n+n'}) D_{nn'} > K_\alpha$</p>
<p>where $n$ and $n'$ are the sizes of samples, D the KS-statistic and $K_\alpha$ the critical value (probably everyone here alr... | g44134 | [
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<p>I'm modeling a set of outcome data the depends on two parameters:</p>
<ol>
<li>time, T</li>
<li>-100 < A < 100</li>
</ol>
<p>I've done logistic regression using R with the command:</p>
<pre><code>model <- glm(Outcome ~ A + T, family = "binomial", data = myData)
</code></pre>
<p>My expectation (the only ... | g61729 | [
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0.004651479423046112,
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<p>I am currently in the process of making a poster presentation and would like some advice (or reference to advice) about some of the aspects of the graphic. For examples posters I am talking about see the supplementary material for the ASA Data Expo articles in <a href="http://pubs.amstat.org/toc/jcgs/20/2">Volume 20... | g61730 | [
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0.02746446058154106,
0.11050180345773697,
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0.04934157803654671,
0.01298... |
<p>I often hear about evaluating a classification model's performance by holding out the test set and training a model on the training set. Then creating 2 vectors, one for the predicted values and one for the true values. Obviously doing a comparison allows one to judge the performance of the model by its predictive... | g61731 | [
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0.03702613338828087,
0.025815410539507866,
0.0... |
<p>I want to cluster a massive dataset for which I have only the pairwise distances. I implemented a k-medoids algorithm, but it's taking too long to run so I would like to start by reducing the dimension of my problem by applying PCA. However, the only way I know to perform this method is using the covariance matrix w... | g61732 | [
0.015678461641073227,
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0.016133874654769897,
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0.005797868128865957,
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0.0010707264300435781,
0.04538280889391899,
-0.009584721177816391,
0.0694698765873909,
0.04... |
<p>What are the steps to obtain the following result:</p>
<p>Given that X have $\Gamma(1,s)$ distribution; and that X=x, and Y have the Poisson distribution with parameter x. Then the characteristic function of Y is:
$\phi_Y(t) = E[E[e^{itY}|X]] = E[exp(X(e^{it} -1))]=(2-e^{it})^{-s}$? </p>
<p>I can't see how to use ... | g61733 | [
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0.0435347817838192,
-0.061752207577228546,
0.037940241396427155,
0.029841119423508644,
0.03066... |
<p>Is there a way to determine the roughness of an n-dimensional optimization surface (n > 3)? Preferably a method that uses measures from fractal geometry/chaos theory...</p> | g61734 | [
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0.008304323069751263,
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0.028076818212866783,
... |
<p>I am very new to R and trying to extract a specific element from a data frame and compare it with an integer. </p>
<p>I had a table saved in text file. </p>
<p><img src="http://i.stack.imgur.com/54dkE.png" alt="data-file image"></p>
<p>I used the following to read the table.</p>
<pre><code>mydata = read.table("f... | g162 | [
0.041766125708818436,
-0.05312402918934822,
0.0017738750902935863,
-0.03368808701634407,
0.02032449096441269,
-0.043474745005369186,
-0.008454118855297565,
0.028370898216962814,
-0.04004107788205147,
-0.004521333612501621,
-0.006515814922749996,
0.04769447073340416,
-0.014293131418526173,
... |
<p>These past few weeks I've been studying statistics more intensely than ever before but I do have some more advanced background in other fields of mathematics such as <em>linear algebra</em>, <em>numerical analysis</em>, <em>differential equations</em>, <em>linear regression</em> (and similar interpolation techniques... | g18480 | [
0.01692805252969265,
0.002166318939998746,
0.013391849584877491,
-0.014089635573327541,
-0.023325355723500252,
-0.013714361935853958,
0.07959463447332382,
-0.004772908985614777,
-0.028630860149860382,
-0.056190941482782364,
0.004498637747019529,
-0.04060792922973633,
-0.009399999864399433,
... |
<p>I'm looking to calculate the standard deviation of a fixed-odds betting proposition. The bet pays 5/6 for a win and you lose your stake for a loss. For a bet of 100, a winner pays 83.33 (and the stake is returned) and a losing bet pays -100. The probability of winning is evens (or very close to evens). </p>
<p>I'm... | g61735 | [
0.019859295338392258,
-0.008287083357572556,
0.025931252166628838,
-0.0004282585287000984,
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-0.023311279714107513,
-0.009684538468718529,
-0.016394076868891716,
-0.0234698299318552,
0.009948530234396458,
0.028931574895977974,
0.005206122063100338,
0.006124278996139765,
... |
<p>I'm dealing with the following situation:</p>
<p>I'm looking at a language at time X and Y. I identify 20 changes between time X and Y. The question is what the best account is for those changes. Theory 1 says it's all due to "external factors", and is able to account for them all in that way: 20/20. Theory 2 says ... | g61736 | [
0.0618848018348217,
0.01912323758006096,
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0.013001197949051857,
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-0.019018732011318207,
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0.015289322473108768,
... |
<p>I have created 3 staffing models - only 2 contain the same parameters. I have determined the costs for implementing all three models. I need to compare the cost of each model to the cost of the current model being used and then compare the costs of each of the 3 models to one another. Is there a way to "standardize"... | g61737 | [
0.005564960651099682,
-0.027052314952015877,
0.00039967597695067525,
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0.034093596041202545,
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0.02891741879284382,
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0.033303845673799515,
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0.018583549186587334,
... |
<p>The paper is:</p>
<p>van den Brink, P.J. & ter Braak, C.J.F. (1999). Principal response curves: Analysis of time-dependent multivariate responses of biological community to stress. Environmental Toxicology and Chemistry, 18, 138-148.</p>
<p>The example data used in the paper:</p>
<pre><code>spdta <- struct... | g61738 | [
-0.0026374130975455046,
-0.07815152406692505,
-0.025351451709866524,
-0.07599083334207535,
0.018649758771061897,
-0.019135307520627975,
0.044747114181518555,
-0.00659331725910306,
-0.032756682485342026,
-0.004504163283854723,
-0.006283326540142298,
0.04610908031463623,
0.05140181630849838,
... |
<p>What is the term $K$ in Akaike information criterion?
The AIC is defined as $2K-2log(L)$, where $L$ is the maximized value of the likelihood function for the estimated model.</p>
<p>On the internet, I found three competing candidates:</p>
<ol>
<li>Number of parameters + error term (for simple linear one-predictor ... | g61739 | [
0.0031707342714071274,
-0.02658909372985363,
-0.010282524861395359,
0.019095594063401222,
0.016124196350574493,
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0.03416866809129715,
0.016079995781183243,
-0.05385158583521843,
0.022090265527367592,
0.001750839757733047,
-0.0038915560580790043,
0.0983346700668335,
-0... |
<p>By "generalized", I mean the circumstance where I have more than 2 periods of time and 2 treatment groups whereas the typical D-I-D model involes just 2 periods, 1 treatment group and 1 control group. Moreover, an individual may jump between these treatment groups, say some observations may fall in treatment group ... | g18481 | [
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0.023667369037866592,
0.03214715048670769,
0.004937812685966492,
0.05243394896388054,
0.0419... |
<p>I want to find anomalies in a time series. Is it possible to find anomalies using moving average?</p> | g49496 | [
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-0.006284150294959545,
0.02118915691971779,
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0.030294237658381462,
-0.006331592332571745,
0.02322334237396717,
0.00930902361869812,
... |
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