question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I'm currently doing my university thesis, and I am unsure what sample size is required in order to achieve an acceptable statistical power. I have recruited them online, via posts on forums and FaceBook. The groups will therefore probably not be even. I currently have 108 participants, though I am unsure who falls i... | g68346 | [
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<p>Some fake data:</p>
<pre><code>X = runif(1000)
ff = rep(1:10,100)
E = rnorm(1000)
y = x+e+f
f = as.factor(ff)
</code></pre>
<p>When you fit a model like </p>
<pre><code>library(mgcv)
m = gam(y~x+s(f,bs='re'),method='REML')
</code></pre>
<p>and </p>
<pre><code>library(lme4)
mr = lmer(y~x+(1|f))
</code></pre>
<p... | g68347 | [
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<p>I'd like to determine the agreement between two lab methods that score samples as 1, 2, 3 or 4. I don't think Spearman-Rho is the right statistical method, is correspondence analysis better? Or something else?
Thanks for your help! </p> | g68348 | [
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<p>I recently bought a fantastic phenomenal book on ARIMA - "Forecasting with Univariate Box - Jenkins Models: Concepts and Cases" by Alan Pankratz. It was originally published in 1983 therefore it does not have the datasets associated with the data sets for practice. Are there any place that someone could recommend ... | g68349 | [
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<p>Let $f$ be a nonnegative function. I am interested in finding $z \in [0,1]$ such that
$$ \int_0^{z} f(x)\,dx = \frac{1}{2}\int_0^1 f(x)\,dx$$ The caveat: all I can do is sample $f$ at points in $[0,1]$. I can, however, choose the locations where I sample $f$ randomly, if I so desire. </p>
<p>Questions:</p>
<ol>
<... | g68350 | [
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<p>For plot 1, I can test the association between x and y by doing a simple correlation.
<img src="http://i.stack.imgur.com/E4fqq.png" alt="plot 1"></p>
<p>For plot 2, where the relationship is nonlinear yet there is a clear relation between x and y, how can I test the association and label its nature?
<img src="http... | g68351 | [
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<p>For a matrix $M$ in which entries $m_{a,b}$ denote the number of co-occurrences between elements $a,b$ from two distinct sets $A$ and $B$, how do I identify pairs with a significantly high co-occurrence? The absolute number of occurrences differs a lot between different $a$ as well as between different $b$.</p>
<p>... | g68352 | [
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<p>What's the most suitable statistical test for testing whether the distribution of the (x,y) coordinates of the blue points is significantly different from the distribution of the (x,y) coordinates of the red points. I'd also want to know the directionality of this difference. The colored data points are those data p... | g68353 | [
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<p>I am very new with statistical programms, statistical analysis and SPSS. Now I even have to use the <code>GEE</code> function which seems to be a little too much for me. Do you have any suggestions on where to find information how to interpret the SPSS output? </p>
<p>So far I am able to interpret the simple OLS re... | g68354 | [
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<p>In R (or generally):</p>
<p>What is the right way to interpret the value of se.fit (standard error of predicted means) from the predict function? When is it appropriate to use se.fit versus residual.scale (residual standard error) of a prediction from a linear regression as the measure for how good a prediction is?... | g68355 | [
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<p>In SPSS, I want to <strong>compare</strong> two clusters of management sciences department faculty members in two universities.</p>
<ul>
<li>Which test should I use?</li>
<li>Can you explain how to do it in SPSS?</li>
</ul> | g68356 | [
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<p>I am reading inference statistics by casella and berger. They are deriving the general formula for the probability distribution like that:</p>
<p>$$EX=\sum_{x=1}^{N}xP(X=x|N)=\sum_{x=1}^{N}x\frac{1}{N}=\frac{N+1}{2} $$</p>
<p>I do not get the step before the result. I would appreciate your explanation on this step... | g68357 | [
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<p>I am trying to work out how to compute the Fisher information for a point process with an event arrival rate of:</p>
<p>$$ \lambda(t) = \mu + \sum\limits_{t_i<t}{\alpha e^{-\beta(t-t_i)}}$$</p>
<p>where $ t_1,..t_n $ are the event arrival times.</p>
<p>The log likelihood function is therefore:</p>
<p>$$ -... | g28350 | [
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<p>this is my first post so let me know if you need more information. This is a pretty general question for now, but I am not sure how to approach this.<br>
The data I have is from an ecological study. In this study, we had two different kind of experimental landscapes, landscape type A and B. We had 8 replicates for l... | g68358 | [
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<p>I'm working on a problem , where a function returns the Log probability of P(X=x) . Now I would like to find the Entropy of X. But since the probabilities I get are log probabilities, again taking its log would be meaningless. One solution That I can think of is converting the probabilities from the log scale to the... | g28351 | [
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<p>Let me ask basic questions.</p>
<p>Q1) What is the difference between cross-correlation between two random variables and cross-correlation between two probability functions for the two random variables?</p>
<p>Q2) In the text book, the cross-correlation between two probability density functions gives joint probabi... | g28352 | [
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<p>Consider an experiment that has four groups, and all of them have experimental replicates.</p>
<ol>
<li>No treatment</li>
<li>Treatment X</li>
<li>Treatment Y</li>
<li>Both X and Y</li>
</ol>
<p>When I fit an interaction model, and check the raw values of the most significant features, I notice a lot of cases wher... | g68359 | [
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<p>I have a general doubt regarding clustering. I have a data set of size 1196*18675. where 1196 is the no of documents. I am trying to cluster the data with k=7 using k-means. Each time the clustered group varies in size.</p>
<p>[iter] c1 c2 c3 c4 c5 c6 c7</p>
<p>[500] 346 233 151 128 126 125 87</p>
<p>[10... | g68360 | [
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<p>I asked the following question in order to gain some intuitive understanding about the d-Separation property in Bayesian Networks a while ago:
<a href="http://stats.stackexchange.com/questions/74093/understanding-d-separation-theory-in-causal-bayesian-networks">Understanding d-separation theory in causal Bayesian n... | g68361 | [
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<p>I am working on a data mining projects and I have to design following type of the model.</p>
<p>e.g.
I have given 4 feature x1, x2, x3 and x4 and four function defined on these</p>
<p>feature such that each function depend upon some subset of available feature.</p>
<p>e.g.</p>
<p>F1(x1, x2) =x1^2+2x2^2 ( Functi... | g28355 | [
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<p>I calculated R square for my neural network based on a formula I found somewhere, which goes something like:</p>
<p><a href="http://i.stack.imgur.com/DojZC.png" rel="nofollow">http://i.stack.imgur.com/DojZC.png</a></p>
<p>It should be something around 0.98-0.99. But, when I operate it on my network, it yields very... | g68362 | [
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<p>It seems to me that ensemble learning WILL always give better predictive performance than with just a single learning hypothesis.</p>
<p>So, why don't we use them all the time?</p>
<p>My guess is because of perhaps, computational limitations? (even then, we use weak predictors, so I don't know).</p> | g68363 | [
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<p>For example, I trained two models: one with SVM and one with KNN.</p>
<pre><code>Final Prediction = 0.4*KNN + 0.6*SVM
</code></pre>
<p>Is this considered blending?</p> | g68364 | [
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<p>I have 2 groups of people.
Both groups have n=35</p>
<p>I go look in the hospital
I do not know how many people are in there,
but I do know that 25% of the sick are from group 1
and 75% of the sick are from group 2.</p>
<p>If things were random, you'd expect the same proportion from each group to exhibit some be... | g68365 | [
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<ol>
<li>the predicted scores on the outcome variable, Ŷ</li>
<li>the residuals</li>
<li>the observed scores on the outcome variable, Y</li>
<li>the standardized regression coefficients </li>
</ol>
<hr>
<p>My understanding is that the question wants to see which of these regression distributions has the greatest spre... | g68366 | [
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<p>I am new to statistics and am in need of some help. I am running a study where I am providing two groups with surveys to test for their perceptions using a Likert Scale. One group I'm testing prior to training, the other after several years of experience. Due to the nature of the position, the sample size is pretty ... | g68367 | [
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<p>This might be a trivial problem but wondering if there's a known model formulation for this problem:</p>
<ul>
<li>Ordered Categorical observed variable with k levels</li>
<li>Trying to estimate the parameter (theta) of a latent Bernoulli/Binomial variable </li>
<li>The latent and observed related by a k-length vect... | g28359 | [
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<p>I played around with some unit root testing in R and I am not entirely sure what to make of the k lag parameter. I used the augmented <em>Dickey Fuller test</em> and the <em>Philipps Perron test</em> from the <a href="http://cran.r-project.org/web/packages/tseries/index.html">tseries</a> package. Obviously the defau... | g68368 | [
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<p>I took a poll of patients who experienced at least one misdiagnosis. I'd like to analyze the data according to gender but 75% of the responses came from Females and 25% from Males.</p>
<p>Example: The data for the misdiagnosis category "IBS" is 4 Males and 19 Females on 19+4=23 total responses.</p>
<p>For Males t... | g5507 | [
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<p>Here is an excerpt from one of the stats books I have been reading:</p>
<p><img src="http://i.stack.imgur.com/ZOkud.png" alt="enter image description here"></p>
<p>But as a counter example, let's suppose we have five possible values for $\theta$ and $\theta_5$ is the ML estimate, with the likelihood 0.4, and we ha... | g68369 | [
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... |
<p>I am learning about the ARIMA model and trying to implement it and had some questions. From my understanding, ARIMA forecasts better for short-term projections rather than long-term projections (is this true or false)? I am implementing the ARIMA to make a 6 month projection on a daily basis. Would I get better resu... | g68370 | [
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<p>Looking for some advice on running simple statistics on some survey data I have. </p>
<p>Part 1. I have two surveys, one from 2009 and one from 2013, with the exact same question but different respondents. How might I compare this question between years to see if they are significantly different or not? The surv... | g68371 | [
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<p>I'm looking to generate fake data to fit a multinomial logit in R? Any code/suggestions on material to look at would be very much appreciated...</p>
<p>Thanks.</p> | g28360 | [
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<p>My ultimate aim is to obtain a model and data for a single univariate time series for the unobservable true price of an item (with minimum error).</p>
<p>Instead of directly observing this true price, I can observe data with the interpretation of this true price by different entities, each of these making up a time... | g68372 | [
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<p>I have the following model:
<strong>y</strong> = P <strong>v</strong> + <strong>n</strong><br>
Where y is the vector of observations, v is a unit vector and n is a Gaussian random noise whose covariance matrix is the identity matrix. P is a positive scalar. All the vectors are reals of size N. </p>
<p>I'd like to ... | g68373 | [
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<pre><code>##Data loading
data(economics)
load(economics)
##Data splitting
Index <- createDataPartition(economics$unemploy, p = 0.8,list = FALSE, times = 1)
head(Index)
train <- economics[Index, ]
test <- economics[-Index,]
## SVM - Regression
svmRbftune <- train(unemploy ~ pce + pop + psavert + ... | g19220 | [
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<p>I want to choose the best random structure for my mixed-effects model. I have compared four models: without a random part, random intercept, random intercept and slope, and random effects:</p>
<pre><code>gls0<-gls(time.dep~exper*group*fat*FL, method="REML",data=test)
lme1<-lme(time.dep~exper*group*fat*FL, ran... | g68374 | [
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<p>Should the target variable in a linear regression be scaled along with the predictor variables? It seems I am getting garbage out if not?</p>
<p>Also what are the differences in log transformation vs the z-score transformation for the variables? Are there situations where one is more appropriate than the other</p... | g49325 | [
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<p>I have really little idea of survival analysis. I am aware that logrank is a special case of Cox' proportional hazards model, and that tons of R packages and scripts address the problem of power / size calculations. However, I didn't manage to make head or tails of all that.</p>
<p>The problem is simple: we have tw... | g28362 | [
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<p>I am currently encountering this problem:</p>
<p>I have an intractable distribution and I want to minimize the KL divergence of this distribution and a Gaussian Copula(or 0 mean gaussian distribution). So we just need to find out the precision matrix.</p>
<p>The distribution is so complicated that it is not really... | g68375 | [
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<p>Suppose you have $n$ objects labeled $1, 2, ..., n$ and $m$ of these objects are chosen with equal probability without replacement. The labels for each of the samples are denoted by $X_1, ..., X_m$. What are some effective ways to estimate $m$ if all you observe are $\min X_i$ and $\max X_i$? </p> | g68376 | [
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<p>With the Data Analysis command in Excel I made a plot, which I can't post, because this is my first post ever.</p>
<pre><code>X - abortions, Y - maternal deaths.
SUMMARY OUTPUT is this:
Regression Statistics
Multiple R 0.796827692
R Square ... | g68377 | [
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<p>I will state the problem in a simplified manner first. Suppose I have two objects, that can be in one of two states. We count the number times when the object is in the second state. The distribution of number of such counts in a time period of length $\Delta t$ is Poisson with intensity $\Delta t\lambda$. The proc... | g38226 | [
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<p>I have a data set containing only categorical variables (both nominal and ordinal in nature). The dependent variable is also ordinal (with 4 categories). I was planning to run a categorical regression with optimal scaling instead of ordinal logistic regression aiming at obtaining a single beta coefficient for each i... | g28364 | [
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<p>Suppose I run a bidirectional stepwise in R with the model:</p>
<pre><code>step(glm(y ~ a + b + c + d, poisson))
</code></pre>
<p>And the result may be:</p>
<pre><code>y ~ d + c
null deviance: 263.6
100 residual degrees of freedom
residual deviance: 132.9
AIC: 648.3
</code></pre>
<p>I read that if you run the li... | g68378 | [
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<p>Suppose we have a hierarchical model regression model (pupils nested in schools) with random intercept for schools. We run a model with data covering a particular period, and observe the variance of the random intercept.</p>
<p>Now we run the same model (same model formulation: ie, same outcome and predictors etc) ... | g68379 | [
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<p>I am putting together a review/meta-analysis of body composition in children. The data I will analyze consists of measures of fat-mass (FM) and fat-free-mass (FFM), which when summed equal total mass. While most papers report the means and SDs for FM and FFM, which is what I want, every so often I get a paper that ... | g68380 | [
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<p>Just 2 simple questions I´m struggling with. Hope you can help.</p>
<p>Suppose that the model $y=\beta X +\epsilon$ with $\epsilon \sim \text{ Normal}(o,\sigma^2I_n)$ has a prior $\beta \sim \text{ Normal}( \beta_0, k(X^TX)^{-1})$</p>
<p>I want two things:</p>
<p>1.) I want to show that for the density of $\beta$... | g28365 | [
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<p>I'm curious about the nature of $\Sigma^{-1}$. Can anybody tell something intuitive about "What does $\Sigma^{-1}$ say about data?"</p>
<p>Edit:</p>
<p>Thanks for replies</p>
<p>After taking some fantastic courses, I'd like to add some cool things about this matrix:</p>
<ol>
<li>It is measure of information, i.e... | g28366 | [
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0.03246142715215683,
0.055909037590026855,
0.0... |
<p>I have a data frame with the following:</p>
<pre><code>> summary(d5$points)
Min. 1st Qu. Median Mean 3rd Qu. Max.
-4.200 0.000 1.000 2.579 5.000 23.400
> sd(d5$points)
[1] 3.736616
</code></pre>
<p>What's a simple, but statistically sound way to categorize this data into <code>terrible... | g19266 | [
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<p>When performing the linear SVM classification, it is often helpful to normalize the training data, for example by subtracting the mean and dividing by the standard deviation, and afterwards scale the test data with the mean and standard deviation of training data. Why this process changes dramatically the classi... | g68381 | [
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<p>I'm fitting a gls following these steps:</p>
<ol>
<li>I select the random effect holding the fixed part unchanged. I.e. I try different variance and correlation structures and random effect.</li>
<li>Once I find my 'good' random component I select the fixed variables I need to have and drop the non significant ones... | g68382 | [
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... |
<p>I'm imputing missing values using <code>R</code>'s <code>mice</code> package. My data has three numeric variables and a class variable so I am using a multilevel imputation with the <code>2l.norm</code> method on the variables. However, like in these <a href="http://stackoverflow.com/questions/20539910/leading-minor... | g68383 | [
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... |
<p>I am using glmnet in R with leave-one-out cross-validation with this command:</p>
<pre><code>cv.fit <- cv.glmnet(trainx, trainy, maxit=10000000, nfolds=NROW(trainy), grouped=FALSE, lambda.min.ratio=20.0^(-3.0), type.measure="mse")
</code></pre>
<p>It produces the information that I want but it also provides a y... | g68384 | [
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<p>Suppose I have two distributions $X$ and $Y$, and I have a statistic $T(X, Y)$. If I have a random sample (iid) $X_1, ..., X_N$ taken from $X$ and a random sample (iid) $Y_1, ..., Y_M$ taken from $Y$, then are the statistics of the cross products (i.e., $\{T(X_i, Y_j) : i \in 1, ..., N, j \in 1, ..., M\}$ a random s... | g19316 | [
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<p>As the title to my question says, I am confused as to when the $R^2$ of a model fit does not equal the slope of the regression between observed and predicted values. </p>
<p>I am trying to present model prediction statistics in a similar way to those presented in the summary figures of the Globcolor validation repo... | g49905 | [
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<p>I have been reading on cook's distance to identify outliers which have high influence on my regression. In Cook's original study he says that a cut-off rate of 1 should be comparable to identify influencers. However, various other studies use 4/n or 4/(n-k-1) as a cut-off.</p>
<p>In my study, none of my residuals h... | g28383 | [
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<p>Are there any major potential problems with using negative binomial regression (xtnbreg) with random effects and lagged dependent/independent variables. (Time-series cross-section data)</p>
<p>I'm analyzing a piece of research that uses time-series cross section data for 138 countries and looks to explain the numbe... | g68385 | [
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<p>I have a choice of Master's programs in statistics, one of which is formally a program in applied statistics, the other is formally in math with an applied statistics "track".</p>
<p>The courses in the 2 programs are about the same, so I am wondering how much the label of the degree really matters (I most likely wi... | g68386 | [
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<p>thank you very much for your time!
I am currently working on a neuroimaging study comparing lateralization indexes between the two hemispheres in three different groups.
I have 4 lateralisation indexes (two different independent parameters for two different fiber tracts) and am now wondering whether it's better to u... | g49529 | [
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... |
<p>I am exploring creating alerts for anomalies in a timeseries. Say that I have a graph like this:</p>
<p><img src="http://i.stack.imgur.com/AEe5G.png" alt="enter image description here"></p>
<p>There are two anomalies here that I would wanted to be alerted on: First, on April 7th with there was a huge spike away fr... | g68387 | [
0.04786457121372223,
0.010927172377705574,
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0.040621813386678696,
0.09470295906066895,
... |
<p>I would like to create a list of columns in SPSS like MACOL1, MACOL2 and up to MACOLn which contain 5 years moving average of a list of Tickers/Symbols/Variables using a short syntax like:</p>
<pre><code>Get Data File
Create
/group of cols of new variables= pma(old group of variables 5)
</code></pre>
<p>and what I... | g37427 | [
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0.04737335443496704,
... |
<p>I counducted a mixed model ANOVA with time as the within subjects variable (3 levels) and group as the between subjects variable (2 levels).
All is significant (time, group, and timeXgroup).
To test if differences over the three times are significant in both groups, I conducted two separate repeated measures ANOVAs,... | g28388 | [
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0.026195507496595383,
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0.013048491440713406,
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0... |
<p>From Wikipedia:</p>
<blockquote>
<p>In k-fold cross-validation, the original sample is randomly
partitioned into k equal size subsamples.</p>
</blockquote>
<p>I am working on a 10 fold cross validation project. I have a dataset that has 76 elements. It means that I can not have equal size partitions. </p>
<p>... | g28389 | [
0.03933435678482056,
0.011767281219363213,
0.016577143222093582,
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0.0039788829162716866,
0.04423864185810089,
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0.02882811240851879,
... |
<p>I have about 5544 runs where I am trying to classify it as failure or success. Here the number of runs that lead to failure is only 64 and rest is sucess. In that case when I try to use SVM should I make the number of classes equal? Will this affect the results?</p> | g49718 | [
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0.0... |
<p>I am using DFA to analyze my data in R. </p>
<p>In SPSS it gives Wilks' $\lambda$ with the output, but in R I couldn't determine how to compute it. I have found code that is available to calculate the Wilks' $\lambda$ value for MANOVA. </p>
<p>I am new to R and it would be helpful if anyone can help me to compute ... | g68388 | [
-0.004832336213439703,
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0.00872646365314722,
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0.10519605875015259,
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-0.04808847978711128,
0.029578223824501038,
0.08509767055511475,
0.0441... |
<p>Specifically, I would like to know what ologit in STATA estimates because I tried a simulation and I had really weird outputs. So I'd like to know how exactly adding a varying term to each threshold e.g. 2*x affects the outcome of the ordered logistic model.</p> | g68389 | [
-0.06871442496776581,
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0.007658747024834156,
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0.002217767760157585,
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0.047699298709630966,
0.08982519805431366,
... |
<p>I am trying to use the <a href="http://www.bioconductor.org/packages/release/bioc/html/limma.html" rel="nofollow">limma</a> package to test some data. The data can have negative values as well as positive values and I'm trying to compare between condition 1 and condition 2. </p>
<p>Example:</p>
<pre><code>librar... | g68390 | [
0.026340126991271973,
-0.029500503093004227,
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-0.04259830340743065,
0.057374194264411926,
-0.026992138475179672,
0.0703306719660759,
0.007195427548140287,
-0.11246141791343689,
-0.02984742447733879,
-0.032732002437114716,
0.06614445149898529,
0.05298276245594025,
0.00... |
<p>If I know that the population is normally distributed, and then take <em>small</em> samples from this population, is it more correct to claim that the sampling distribution is <strong>normal</strong> or instead follows the <strong>t distribution</strong>?</p>
<p>I understand that small samples tend to be t distribu... | g28398 | [
0.055788543075323105,
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0.012628181837499142,
0.009111901745200157,
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0.05264617130160332,
-0.012622973881661892,
0.04398186877369881,
0.019201703369617462,
-0.024908244609832764,
0.045183081179857254,
-0.036148201674222946,
0.005841203033924103,
-0.... |
<p>A somewhat basic question here: Is there a recommended minimum number or percentage of observations that needs to be in one category of a dummy variable used as a predictor in multiple regression? I read somewhere that there must be at least a 90:10 spread of observations between the two categories. Is this true?</p... | g28399 | [
-0.0038953081239014864,
0.004607447423040867,
0.007520442828536034,
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0.004567255266010761,
0.029849940910935402,
-0.007482087705284357,
-0.052467260509729385,
0.04508983716368675,
0.03533797711133957,
0.043173421174287796,
0.... |
<p>A few days ago I saw a post on how to setup a SweaveR, which would allow for a user to directly export things like tables, graphs, etc. into Latex. I couldn't quite follow the directions. </p>
<p>Can anyone give step-by-step instructions on how to do it on both, Mac and Windows?</p> | g38260 | [
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0.015098714269697666,
0.09000048786401749,... |
<p>I'm trying to solve a problem for least angle regression (LAR). This is a problem <strong>3.23</strong> on page <strong>97</strong> of <a href="http://www.stanford.edu/~hastie/local.ftp/Springer/ESLII_print5.pdf#page=115" rel="nofollow">Hastie et al., Elements of Statistical Learning, 2nd. ed. (5th printing)</a>.</p... | g68391 | [
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0.02171015553176403,
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0... |
<p>Let Year 1 be last year's data and Year 2 be this year's data. </p>
<p>Suppose that in Year 1, you had a likert scale that was 1-9 (Categorical/Ordinal) and that in Year 2, for the same question you had a likert scale that was 1-5 (Categorical/Ordinal). </p>
<p>What would be some of the things that you would try (... | g68392 | [
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0.014466878026723862,
0.04017028585076332,
0.04113848879933357,
0.0989040732383728,
0.0... |
<p>I have several time series (generated from a numerical model) that go through an initial stage of spinup, followed by a period of dynamic equilibrium, that presumably exists for all times beyond the spinup period. <a href="http://26.media.tumblr.com/tumblr_lfyplfPp1J1qgj7hyo1_500.png" rel="nofollow">See this link fo... | g28404 | [
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0.01397184282541275,
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0.06356038898229599,
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0.017803318798542023,
0.05841241404414177,
0.01... |
<p>I have found contradicting interpretation guidlines and wanted to clarify (using SPSS):
I have a 2x2 design, so 2 categorical factors with 2 levels each and want to test for group differences on my continuous DV. As I have heterogenous variances, I wanted to run regressions in SPSS, because bootstrap-results for the... | g17651 | [
-0.03455173224210739,
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-0.01829814910888672,
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0.07627740502357483,
0.0221047755330801,
0.0295642... |
<p>Can anyone suggest me, which Mathematical(Statistical) methods can be used to predict <code>incoming</code>calls by a given time interval at a call centre? Please cite any research paper or a website that may help in this kind of forecasting. </p>
<p>Can incoming calls be treated as a<a href="/questions/tagged/pois... | g16910 | [
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0.01705247163772583,
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0.0551036074757576,
... |
<p>I have a more conceptual/heuristic question about how to go about formulating a problem in order to take a semi- or unsupervised method of solving it. I'm working on a project with data collected through a mobile app that allows cyclists to track their rides. Much of this dataset is comprised of coordinate (lat, lon... | g68393 | [
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0.029372453689575195,
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0.0... |
<p>Suppose we have $N$ independent random variables $X_1, \cdots, X_N$ drawn from $f_1 > \cdots > f_N$ where $f_i > f_j$ indicates that $f_i$ and $f_j$ satisfy the monotone likelihood ratio property (MLRP). That is, $\forall a<b$ $$ \frac{f_j (a)}{f_j (b)} > \frac{f_i(a)}{f_i(b)}$$.</p>
<p>Now suppos... | g68394 | [
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0.008783536963164806,
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0.007006414234638214,
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0.011884661391377449,
0.01903221569955349,
-0.06300529092550278,
-0.002557438565418124,
-0.021858839318156242,
... |
<p>Consider the polynomial kernel: $$K(\boldsymbol{x}, \boldsymbol{x}') = (\boldsymbol{x}^{T} \boldsymbol{x}'+c)^{d}$$</p>
<p>What exactly is the role of $c$? If $c$ is large, does this indicate that lower order terms play an important role in determining the similarity of $\boldsymbol{x}$ and $\boldsymbol{x}'$?</p> | g68395 | [
0.02359239012002945,
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<p>Consider a classification problem in which the raw data are snippets of a larger 1-D time series signal. In my application, the signal is the response of a motion sensor as a function of time (the raw measurements themselves are voltages).</p>
<p>One "sample" for classification purposes will be some subsampled wind... | g68396 | [
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0.030941946431994438,
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<p>My basic knowledge on model simplification comes from Crawley (2007) and I have also looked in Zuur et al Mixed Effects Models and Extensions in Ecology with R to try to answer my question.</p>
<p>In summary my question is - is creating a new categorical variable which combines two levels with similar coefficients,... | g68397 | [
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0.... |
<p>I have a binary logistic regression model with a McFadden's pseudo R-squared of 0.192 with a dependent variable called payment (1 = payment and 0 = no payment). What is the interpretation of this pseudo R-squared? </p>
<p>Is it a relative comparison for nested models (e.g. a 6 variable model has a McFadden's pseudo... | g34362 | [
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0.08704709261655807,
-... |
<p>I have study on catch for tuna longline. In here I have 3 independent variables (number of hooks, length of branch line & baits) and 3 dependent variables (catch of tuna, catch of marlin & catch of shark).</p>
<p>So what statistics should I use if I want to know:</p>
<ol>
<li>The effect of different baits ... | g68398 | [
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0.010298294946551323,
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<p>I realise that there are 3 tuning parameters in the boosting trees model, i.e. </p>
<ol>
<li>the number of trees (number of iterations)</li>
<li>shrinkage parameter</li>
<li>number of splits (size of each constituent trees)</li>
</ol>
<p>My question is: for each of the tuning parameters, how should I find its opti... | g28413 | [
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0.04998202621936798,
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0.05367501080036163,
0.04076692834496498,
0.05... |
<p>Basically I want to classify a rather rare status (about 2% of the 2000) with some predictors. I have used logistic regression, neural network, and Support Vector Machines to do it. </p>
<p>All the predictors in the logistic regression are statistically significant. And to avoid overfitting, I have self-implemented... | g68399 | [
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<p>I have a time series dataset which shows, for each day, the number of complaints received by an organization about a particular problem. I also have a number of other time series for the same period (mostly environmental variables like weather, chemistry etc.) which may help to explain the pattern of complaints.</p>... | g68400 | [
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<p>I am trying to recreate what my predecessor has done, with the only knowledge being he used "regression."</p>
<p>I'm predicting my dependent variable based on the day of the week, but also on two other quantitative variables. I initially intended to use indicator variables for the week day, but then remembered that... | g28414 | [
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<p>My two separate response (dependent) variables are counts of two mesopredator grouper species on coral reefs. I have tried various models (LM, GLM Poisson and Gaussian and zinf and zinb) both with untransformed response variables and with square root transformed response variables. </p>
<p>The best fit model for o... | g28415 | [
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<p>I have a dataset that contains 100 different patients over 5 year’s period. Every patient is examined each month with regard to particular illness and marked as healthy or ill (0 or 1). Every person appears 60 times in my sample (5 * 12 = 60).</p>
<p>Every month patient provides A = Average blood pressure in that m... | g28417 | [
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<p>Which of the following is a data mining task? Select one:</p>
<p>A. Search Google for “Indian National Flag”.</p>
<p>B. Giving a 100% correct prognosis of the future success or failure for a new business.</p>
<p>C. Grouping search results by theme of the results.</p>
<p>To the extend I have understood about DM I... | g68401 | [
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<p>I am working on a regression modelling approach to predict the health status of samples (disease vs no disease). I already have some evidence of the number of genes involved (numeric variable) is significant in predicting the status, and of one particular gene (gene G) being particularly involved in determining dise... | g68402 | [
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0.06159592419862747,
0.069... |
<p>I am quite confused at the moment regarding multilevel models as implemented in SAS PROC MIXED. I am new to mixed models.</p>
<p>Let's say I have 2 treatments, a new treatment and a control. And let's say that I have a sample of n subjects, each is contributing 1, 2 or 3 samples, i.e., the treatment (new or control... | g68403 | [
0.0198430847376585,
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0.0352136604487896,
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0.0177... |
<p>My question is twofold and concerns weighting in multilevel models and using factor scores as predictors on level 2.</p>
<p>Here is my problem: I want to estimate (using the meologit command in Stata 13) a multilevel model with a ordered categorical dependent variable. My data are persons (N=34500) nested in zip-co... | g68404 | [
-0.041062429547309875,
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0.06563705205917358,
... |
<p>I am looking for a way to conduct sequential (dynamic) MDS based on several variables coded for a sequence of stimuli. Could anyone direct me to software for this purpose (especially R packages / code)?</p> | g68405 | [
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0... |
<p>I took a sample from the university, but I stipulated that the sample students have to be at a specific mental age: 19 at the first year. The number of all students at the 1 year is known, but the size of the students at the age of 19 at the 1 year is unknown, I took the sample through searching for the students w... | g28422 | [
0.004255365114659071,
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0.007144608069211245,
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0.01053778175264597,
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0.026318803429603577,
0.01... |
<p>I recently read an approach which is used to find the effect of changing an independent variable.</p>
<p>They are doing a classification problem, so each data row (or record) is associated with an outcome of YES or NO.</p>
<p>They take one data row (i.e., test row), and then build a model using the other n-1 rows ... | g68406 | [
-0.02951514534652233,
-0.04706544056534767,
0.012245440855622292,
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0.012302679941058159,
0.04642350226640701,
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0.005530318710952997,
0.0290866456925869,
0.03162428364157677,
0.05579417571425438,
0.0075... |
<p>I hope this one is self-explanatory, but let me know if something is unclear: Is there a multivariate version of the Weibull distribution?</p> | g28424 | [
0.02148524299263954,
0.033176813274621964,
-0.021051140502095222,
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0.009593505412340164,
... |
<p>I'm trying to fit raw data to curves, which works well on an individual basis. However, I'd like to "share" parameters (sometimes referred as nested parameters) across more than one data series. Is there a way to do this in R?</p> | g68407 | [
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0.0784218385815620... |
<p>I have a good handle on probability theory, at least I understand the book I <strong>1st course in probablity</strong> by Ross. </p>
<p>However, I am having a hard time understanding Statistics, I got a prep book to teach me but it seems to be just logical deductions are given as the reason for why $\frac{\sigma}... | g68408 | [
0.032368406653404236,
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0.04579036310315132,
0.0... |
<p>My question is simply, why is the <a href="http://en.wikipedia.org/wiki/Geometric_median" rel="nofollow">geometric median</a> called the $L_1$ estimator? This always reminds of $L_p$ spaces but the distance being minimized in the geometric median's definition isn't $L_1$ but rather the $L_2$ (Euclidean) norm. What d... | g11581 | [
0.022021520882844925,
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0.030932243913412094,
0.029431762173771858,
0.05074850097298622,
0.0... |
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