question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have been running a multiple moderator analysis in a pretty simple model.</p>
<p>X are Google search queries normalized to 0-100.
Y are the new registrations of cars in one country
and one moderator.</p>
<p>After checking for normality of the dependent variable Y, the result has been that it is skewed to the le... | 36,799 |
<p>I would like to evaluate the goodness-of-fit of the following (<em>Pareto</em>-like) distribution:
$$
f(r) = \sigma \centerdot r^{-\rho}
$$
The function estimates the population of cities given the rank $r$ in a popularity ranking.</p>
<p>I have not estimated the parameters ($\sigma$ and $\rho$) from the sample. Ho... | 74,130 |
<p>I am curious to know exactly, what are the (possible) differences between inductive and deductive statistical inferences in applied statistics.</p>
<p>Suggestions for some good resources to learn their differences, pros and cons properly are greatly appreciated. </p> | 36,801 |
<p>I have several markets across the US where a marketing program was launched, and I want to compare the mean weekly unit sales before and after the launch. I'm using the 10-weeks prior to launch as my baseline and the 10 weeks post-launch as my result. Now at the end I will use a paired t-test to compare the change ... | 74,131 |
<p>Its been a while since I did any serious statistics. I have been reading about contingency tables recently and it seems like they may offer a solution to my problem. There are people on here that know more about statistics than what I can ever expect to know, so rather than trying to "discover" things by myself, (an... | 36,803 |
<p>Say I have a random vector $Y\sim N(X\beta,\Sigma)$ and $\Sigma\neq\sigma^2 I$. That is, the elements of $Y$ (given $X\beta$) are correlated.</p>
<p>The natural estimator of $\beta$ is $(X'\Sigma^{-1}X)^{-1}X'\Sigma^{-1}Y$, and $\text{var}(\hat{\beta})=(X'\Sigma^{-1}X)^{-1}$</p>
<p>In a design context, the experim... | 74,132 |
<p>My apologies if this has been answered here. It's my first time here.</p>
<p>I am a developer by trade. I am not really into this thing, but I was asked to do some data simulation using SPSS. But I am not sure what significance level to use. I was given a small data set of 24 cases. This is medical research so I as... | 36,804 |
<p>I asked a question earlier in the forum on auto arima click here <a href="http://stats.stackexchange.com/questions/68261/performance-evaluation-of-auto-arima-in-r-and-ucm-on-one-dataset">Performance evaluation of auto.arima in R and UCM on one dataset</a>. The auto.arima provided strange forecast, upon further looki... | 49,926 |
<p>Many of the questions I've posted on SE in the last month have been in the goal of helping me solve this particular problem. The questions have all been answered, but I still can't come up with a solution. So, I figured that I should just ask the problem I'm trying to solve directly. </p>
<p>Let $X_n \sim F_n$, ... | 49,160 |
<p>I've been studying both discrete- and continuous-time Markov chains under stationarity assumption. Now I'm trying to move to non-stationary Markov chains. I did some google search and checked both Ross and Karlin on stochastic processes, but couldn't find anything. I'm hoping that someone can provide me with some re... | 74,133 |
<p>When teaching regression, I used to do an exercise where students would try to guess where the line of best fit is on a scatterplot, and get the sums of squares. They'd move the line around, see how the slope and intercept changed, and see how the sum of squared residuals changed.</p>
<p>It shows that the line of b... | 74,134 |
<p>I have this statement, but I want to be able to add a probability statement to it, like "I'm 87% sure.."</p>
<p>Here is the data I have</p>
<blockquote>
<p>I'm 100.00% sure that grpn will go down the next day, because it's happened 3 of the last 3 times.<br>
Min move of 0.66%<br>
Max move of 16.54%<b... | 36,808 |
<p>I am using a relevance vector machine as implemented in the kernlab-package in R, trained on a dataset with 360 continuous variables (features) and 60 examples (also continuous, so it's a relevance vector regression).</p>
<p>I have several datasets with equivalent dimensions from different subjects. Now it works fi... | 74,135 |
<p>When preparing a summary document for policy-makers, it's fairly common to include a graphic that represents how the optimal policy solution varies with two variables. It may be the result of a formal or informal optimisation analysis. Below is an example of such a graphic. The graphic partitions the chart area into... | 74,136 |
<p>I am new to R. I am building predictive model with gbm package. I have a problem that I retrieve different results for data from data frame that was used for building of the model and for separate data frame with same values.</p>
<p>I randomly divide my data to two sets, training set is loaded to `head':</p>
<bloc... | 36,809 |
<p>I am trying to build an index that summarizes health care quality on different departments for a number of hospitals. I have selected a number of variables, each representing quality in a medical specialization.</p>
<p>The weighting scheme is quite obvious for me. Since the index will be related to costs on an aggr... | 74,137 |
<p>I am working on a model which predicts a binomial variable. I have millions of records and hundreds of variables to sample from. I have millions of records from individuals from each of the past several years. Most of the variables have specific data to the individual and to the year. However I do have a few var... | 35,031 |
<p>I am reading about influence diagrams, and I want to know how their utility function is calculated.</p>
<p>In all of the examples listed in the literature, I am not able to find the formula of the utility function.</p> | 74,138 |
<p>am doing my dissertation involving cox model and i would like to understand how you interpret the survival table at mean of covariates. how i do u i determine the survival function from the output</p>
<pre><code>Survival Table
At mean of covariates
Time Baseline SurvivalSE Cum Hazard
0 .023 .991 .006 ... | 25,389 |
<p>I turn to this forum for advice with the following problem. If you could please shed some light on any aspect of this question I'd be very grateful.</p>
<p><strong>Problem decription:</strong><br>
I'm trying to use an SVM to segment a grayscale image of a puncture in polymer (original res. 1280x1024, can't post, no... | 36,817 |
<pre><code>library(mvtnorm)
set.seed(1)
x <- rmvnorm(2000, rep(0, 6), diag(c(5, rep(1,5))))
x <- scale(x, center=T, scale=F)
pc <- princomp(x)
biplot(pc)
</code></pre>
<p><img src="http://i.stack.imgur.com/Jj6C7.png" alt="enter image description here"></p>
<p>There are a bunch of red arrows plotted, what d... | 36,818 |
<p>I am conducting an ordinal logistic regression. I have an ordinal variable, let's call it Change, that expresses the change in a biological parameter between two time points 5 years apart. Its values are 0 (no change), 1 (small change), 2 (large change).</p>
<p>I have several other variables (VarA, VarB, VarC, VarD... | 74,139 |
<p>I'm a bit of a novice at maths and am trying to get my head around a problem.</p>
<p>I have 3 independent variables which affect 1 dependent variable. I want to create a 4D model which will give me the 4th dimension when I give it an (x, y, z) triplet. </p>
<p>I am programming in Java and already have a regression... | 37,613 |
<p>I was wondering what relations and differences are between pivotal statistic versus distribution free statistic?</p>
<ol>
<li><p>From <a href="http://en.wikipedia.org/wiki/Pivotal_quantity" rel="nofollow">Wikipedia</a></p>
<blockquote>
<p>a pivotal quantity or pivot is a function of observations and unobservabl... | 74,140 |
<p>Quick background:</p>
<p>I am working on a political science project that involves analyzing the impact of different variables on the extent to which a candidate mentions other users when he or she tweets. </p>
<p>One of these variables is whether the candidate answers the Political Courage Test (PCT). If he/she d... | 74,141 |
<p>I have some data gathered from a survey conducted within my city. All responses include an approximate geo location of where they were gathered (accurate to probably a couple of hundred yards which is relatively small), and things like the respondents age, sex, income range, number of dependents, etc. There are appr... | 74,142 |
<p>I am doubting myself on which analysis to run for the following:
18 participants were evaluated at 4 time points with different conditions at each time.
They were given scores (on a discrete visual analog scale) by 2 raters.</p>
<p>The scores were calculated for a pair of participants: the pairs changed at each tim... | 37,931 |
<p>I have an experimental sample, size of about 1000 values. I need to generate a much larger sample for simulation. I can create a samples like this:</p>
<pre><code>library(ks)
x<-rlnorm(1000)
y<-rkde(fhat=kde(x=x, h=hpi(x)), n=10000, positive = TRUE)#
z<-sample(x, 10000, replace = TRUE)
par(mfrow=c(3,1))... | 36,822 |
<p>I am required to use the Naive Bayes classifier to classify example 8, to see whether it is poisonous or not. </p>
<p><img src="http://i.stack.imgur.com/SnscY.png" alt="enter image description here"></p>
<p>I gained the following results:</p>
<p>p(x|Poisonous=Y) = 0.0267857 and </p>
<p>p(x|Poisonous=N) = 0.01019... | 36,823 |
<p>This is probably a far too basic question for this board - but on the other hand, I know I'll get good answers. "Stats 101" is a metaphor, by the way. I'm asking for help with my work, not my homework!</p>
<p>I am looking at aggregate financial data for hospitals. I have identified two hospital systems that accu... | 38,185 |
<p>I wonder if <a href="http://en.wikipedia.org/wiki/Categorical_data" rel="nofollow">categorical data</a> by definition can only take finitely or countably infinitely many values? And no more i.e. not uncountably many values? </p>
<p>Related question: is the distribution of a categorical variable always a discrete di... | 74,143 |
<p>I'm trying to implement an ordered probit model in pymc, and I'm stuck. The model is similar to <a href="http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCkQFjAA&url=http://www.vision.caltech.edu/visipedia/papers/WelinderEtalNIPS10.pdf&ei=fj17T-CvCoek8QS5--HTBA&am... | 36,825 |
<p>For a method calculating expected claims in insurance I have to assume lognormal distribution. For testing I would use annual cumulated data. With a small sample capped at 20 years, my idea is to use disaggregated data - monthly, or individual claims. Now I have found hat the sum of lognormal claims is not a lognorm... | 36,826 |
<p>What are hierarchical priors? </p>
<p>How do they differ from the general concept of priors?</p> | 36,827 |
<p>I'm currently storing the following things in my Database about user submitted content:</p>
<ul>
<li>Downloads: The total Download count of the Content</li>
<li>Likes: A user can either like a content or do nothing</li>
</ul>
<p>How can I determine which Content has got the highest popularity by using these two nu... | 36,828 |
<p>I need to test for correlation of 4 sets of weather parameters between 2 sites. I am not interested in interactions between the parameters. Because no weather parameter is independent from other weather parameters, if I was simply trying to determine if each parameter differed between the 2 sites, I would use a MANO... | 74,144 |
<p>I have two questions related to cross validation in LIBLINEAR </p>
<p>I have 1000 documents from which i take 300 documents for training and rest 700 for classification .
I train 300 documents with parameter -s 0 having two class labels and then while prediction i feed 700 one by one document to the classifier w... | 76 |
<p>So, I think that I have a decent grasp of the basics of frequentist probability and statistical analysis (and how badly it can be used). In a frequentist world, it makes sense to ask such a question as "is this distribution different from that distribution", because distributions are assumed to be real, objective an... | 74,145 |
<p>I've been reading the <a href="http://en.wikipedia.org/wiki/Levene%27s_test" rel="nofollow">Wikipedia page</a> for Levene's test, and it cites the degrees of freedom as (k - 1, N - k), where k is the number of different groups to which the sampled cases belong, and N is the total number of cases in all groups. Howe... | 6,937 |
<p>I am particularly interested in hearing thoughts on what are logical next steps in the research agenda of people who are interested in "The experimental approach to development economics" or in the evaluation of policy.</p>
<p>Many people reject the notion that a randomized controlled trial (RCT) can estimate relev... | 48,513 |
<p>Akaike's model selection criterion is usually justified on the base that the empirical risk
of a ML estimator is a biased estimator of the true risk of the best estimator
in the parametric family, say the family of linear regressors on a m-dimensional variable,
$S_m $</p>
<p>On the other hand, this family, $ S_m$,... | 36,839 |
<p>I am using R, I searched on Google and learnt that <code>kpss.test()</code>, <code>PP.test()</code>, and <code>adf.test()</code> are used to know about stationarity of time series.</p>
<p>But I am not a statistician, who can interpret their results</p>
<pre><code>> PP.test(x)
Phillips-Perron Unit Root Tes... | 36,841 |
<p>I have responses to a questionnaire item from a number of people, measured at equidistant timepoints. I wish to fit a growth mixture model (in R, using the LCMM package) to this data to find latent classes. My data looks something like this:</p>
<pre><code> ID item-response timepoint
----------------------... | 74,146 |
<p>I have web log analysis data (AWStats) from a university library website. I'm looking at the number of visits per month divided by the number of faculty plus student enrollment (visits per headcount). This shows a downward trend, along with strong seasonality. Also, the undergrad enrollment has gone up steadily the ... | 74,147 |
<p>Let $X_{n}$ be an $\mathcal F_{n}$-martingale and let $B\in \mathcal B$.<br>
Show that $T=\min\{n:X_{n}\in B\}$ is an $\mathcal F_{n}$-stopping time.<br>
$\mathcal B$ is Borel $\sigma$-algebra and filtration is $\mathcal F=\sigma(X_{1},\dots,X_{n})$.
Thanks for help.</p> | 74,148 |
<p>I was just wondering if someone could help me understand this derivation of the probability generating function for a Poisson distribution, (I understand it, until the last step):</p>
<p>$$\pi(s)=\sum^{\infty}_{i=0}e^{-\lambda}\frac{\lambda^i}{i!}s^i$$
$$\pi(s)=e^{-\lambda}\sum^{\infty}_{i=0}\frac{e^{\lambda s}}{e^... | 36,844 |
<p>I have a cycle that I filtered out from an original series using a Baxter deterministic filter. However, the cycle plot still has some noise and I would like it to be more determinisitc and follow a perfect sinosiod. I can run a trig-regression of the cycle on a $\sin(2\pi\cdot\text{index}/12)$ but I wouldn't know ... | 36,845 |
<p>Given the number of users of an application was 70 in total, it's <a href="http://www.measuringusability.com/five-users.php" rel="nofollow">my understanding that research shows</a>:</p>
<blockquote>
<p>Five users is the number of users needed to detect approximately 85%
of the problems in an interface, given th... | 74,149 |
<p>Is there any interesting problem in the area of "Document Image Analysis and Retrieval" which by nature needs an online/incremental clustering process ? The problem may be in the context of "Logical Structure Analysis", or "Document Layout Analysis" to identify regions of interest in a scanned page, or any other rel... | 36,848 |
<p>I want to test the influence of exchange rates on a price index and struggle with the interpretations. My variables are I(1)</p>
<p>First, I ran an OLS on first differenced variables which indicated a negative short term relation between FX and PI. Then, I tested it on co-integration and constructed a VECM.</p>
<... | 74,150 |
<p>Here is the problem (not homework),</p>
<p>Let $U_1,\cdots,U_n$ be i.i.d. uniform$(-n,n)$ random variables.
For $-n<a<b<n$, we set $1_{U_i}(a,b)$ be the indicator function such that $1_{U_i}=1$ if $U_i\in(a,b)$ and 0 otherwise. What is approximate distribution as n large of $U_1+,\cdots,+U_n$.</p>
<p>I c... | 74,151 |
<p>I was recently looking for ways to resample time series, in ways that</p>
<ol>
<li>Approximately preserve the auto-correlation of long memory processes.</li>
<li>Preserve the domain of the observations (for instance a resampled times series of integers is still a times series of integers).</li>
<li>May affect some ... | 36,850 |
<p>I have two variables that predict fraud behavior (dependent variable). The independent variables are perception of fraud being wrong (1-5) and probability of being caught (1-5). The dependent variable is frequency of committing fraud in the last 5 years (never, once, 2-3 times, 4 times and more).
Two questions: </p... | 36,851 |
<p>I need to explain the concept of linear mixed models in an article targeted at a mainstream audience. Is there a way of communicating the gist of the concept in a sentence or two?</p> | 36,852 |
<p>Consider approximating the following expectation:
$$\mathbb{E}[h(x)] = \int h(x)\pi(x) dx$$</p>
<p>Where $h(x)$ is an arbitrary function and $\pi(x)$ is a distribution for which the <strong>normalizing constant is not known</strong>. Also, assuming the above integral is highly variable and high dimensional the stan... | 74,152 |
<p>I am working with a batch of about 1000 univariate time series in R . For every time series, I have to perform following tasks , before deciding upon a model be it ARIMA, TAR or Holt Winter's Model </p>
<ol>
<li>Trend Detection and its type , i.e. whether trend is deterministic or stochastic</li>
<li>Seasonality D... | 74,153 |
<p>How to calculate uncertainty of linear regression slope based on data uncertainty (possibly in Excel/Mathematica)?</p>
<p>Example:
<img src="http://i.stack.imgur.com/duJ8T.jpg" alt="Example plot">
Let's have data points (0,0), (1,2), (2,4), (3,6), (4,8), ... (8, 16), but each y value has an uncertainty of 4. Most f... | 74,154 |
<p>I just realised that even though I know how to perform an independent samples t-test or a Mann whitney test, I am not sure how their results should be reported in a paper.
I was given this study to read in preparation for a Research Methodology class but it does not report the "easy" tests, so I wonder.</p>
<p>Edit... | 74,155 |
<p>As per Wikipedia, I understand that the t-distribution is the sampling distribution of the t-value when the samples are iid observations from a normally distributed population. However, I don't intuitively understand why that causes the shape of the t-distribution to change from fat-tailed to almost perfectly normal... | 913 |
<p>Suppose I have a Netflix-style recommendation matrix, and I want to build a model that predicts potential future movie ratings for a given user. Using Simon Funk's approach, one would use stochastic gradient descent to minimize the Frobenius norm between the full matrix and the item-by-item * user-by-user matrix com... | 74,156 |
<p>I'm working with a survey that uses a rolling data collection format (i.e., there are multiple waves of sampling and initial contacts). I'm trying to develop a model to predict how likely a sample member is to respond to the survey within 7 weeks from today. Predicting whether a respondent who is first contacted tod... | 74,157 |
<p>Suppose we have $p$ dimensional vectors $Y_i$ which we model with $f_Y (y |\theta) = \sum \pi_k N(y | \mu_k, \Sigma_k)$ with $\theta$ being a catch all for the model parameters (the number of components might be a finite known/unknown number or infinite as in Dirichlet process mixtures). The prior on $\pi$ will eith... | 48,548 |
<p>Given a set of extracted data from different sources with different accuracies, how can I combine the accuracy of those who give the same output?</p>
<p>Example :</p>
<pre><code>Data from source A are 80% correct
Data from source B are 85% correct
Data from source C are 90% correct
</code></pre>
<p>If two of the ... | 74,158 |
<p>I'm working on an ongoing data analysis project about a series of live educational seminars. Each of my data points represents one such event, and for each one I have a multitude of categorical variables, as well as a couple quantitative ones that are my desired response variables (total revenue and number of attend... | 48,550 |
<p>I've fit a mixed linear model to some longitudinal data. I'm interested in the differences in patterns of decrease in the dependent variable according to group status, and my hypothesis particularly predicts a difference between the groups in trajectory of change at between specific ages. The data shows a significan... | 36,868 |
<p>I recently read a paper made a logistic regression and used a table like this to summarise the model:</p>
<pre><code>data.frame(predictors = c("drat", "mpg"), "chi squared statistic" = c("x", "x"), "p-value" = c("x", "x"))
predictors chi.squared.statistic p.value
1 drat x x
2 ... | 74,159 |
<p>Actually I thought Gaussian Process is a kind of Bayesian method, since I read many tutorials in which GP is presented in Bayesian context, for example, in this <a href="http://see.stanford.edu/materials/aimlcs229/cs229-gp.pdf" rel="nofollow">tutorial</a>, just pay attention to page 10.</p>
<p>Suppose the GP prior ... | 74,160 |
<p>I have a two data-sets of a set of subjects with values for their baseline and followup visit. I would like to do a repeated measure test to see whether there is a significant difference between the two sets (baseline & followup). I know I can do a simple paired t-test. But I need to adjust my values for covaria... | 74,161 |
<p>I'm studying regression analysis but I'm struggling with really understanding how degrees of freedom are calculated. For example, if we have the simple scenario where $Y_i=\beta_0+\beta_1 X_i + \epsilon_i$ (and all the standard assumptions hold) then I read</p>
<p>$\frac{1}{\sigma^2} \sum_{i=1}^n (\hat{Y}_i - \bar... | 74,162 |
<p>I have a problem with logistic regression.
I had found out (<a href="http://www.uk.sagepub.com/burns/website%20material/Chapter%2024%20-%20Logistic%20regression.pdf" rel="nofollow">here</a>) that one of the assumptions of logistic regression model should be min. of for example 50 observations per predictor. But if ... | 74,163 |
<p>I am an ml noob. I have a task at hand of predicting click probability given user information like city, state, os version, os family, device, browser family browser version, city, etc. I have been recommended to try logit since logit seems to be what MS and Google are using too. I have some questions regarding logi... | 74,164 |
<p>My response variable is number of Fishing cat scats and I am using a zero-inflated poisson regression model to see the effect of the predictor variables on habitat use of Fishing
cats. The predictor variables are Reed area, Vegetation Area and Agricultural area. </p>
<p>Now, before using the GLM, I used scatterplot... | 36,880 |
<p>I'm trying to find a test that will allow me to test the relationship between a categorical dependent variable and several independent variables that are both continuous (interval) and ordinal. </p>
<p>If there is no such test, it would also makes theoretical sense for me to turn the variable "around". That is, I c... | 74,165 |
<p>I am calling the R MICE routines into SPSS to do multiple imputations. My question is how to save the multiple imputed data sets as SPSS files for later analyses.<br>
Any help would be greatly appreciated.</p>
<p>DLuo</p> | 74,166 |
<p>I originally planned on path analysis utilizing multivariate multiple regression to test my hypothetical model - but I am not getting my sample size. I have looked at non-parametric regression techniques but - am not sure how I can develop my model using these techniques - or if a path model would even be useful at ... | 74,167 |
<p>I am trying to fit a multi-group latent growth curve model using censored data in Mplus. I have been able to fit a multi-group model using uncensored data, and a single group model using the censored data. Is there a way to combine these?</p>
<p>When I have tried to combine these, the error message suggests using K... | 74,168 |
<p>I have used Kendall's tau to examine whether there is a correlation between a number categorical variables, as I have a small sample. However, I also want to test whether some variables might have an confounding effect on some of the relationships. Unfortunately, with SPSS you can only use partial correlation using ... | 74,169 |
<p>I'm having issues forecasting a model of the following form.</p>
<pre><code>y1 <- tslm(data_ts~ season+t+I(t^2)+I(t^3)+0)
</code></pre>
<p>It fits my data very well, but I run into a problem when attempting to do this:</p>
<pre><code>forecast(y1,h=72)
</code></pre>
<p>This is the error that R gives me.</p>
<... | 74,170 |
<p>Can anyone report on their experience with an adaptive kernel density estimator?<br>
(There are many synonyms:
adaptive | variable | variable-width, KDE | histogram | interpolator ...)</p>
<p><a href="http://en.wikipedia.org/wiki/Variable_kernel_density_estimation" rel="nofollow">Variable kernel density estimation<... | 74,171 |
<p>I've got a model that I've developed in R, but also need to express in SAS. It's a double GLM, that is, I fit both the mean and (log-)variance as linear combinations of the predictors:</p>
<p>$E(Y) = X_1'b_1$</p>
<p>$\log V(Y) = X_2'b_2$</p>
<p>where Y has a normal distribution, $X_1$ and $X_2$ are the vectors of... | 74,172 |
<p>Let random variables $X$ and $Y$ be independent Normal with distributions $N(\mu_{1},\sigma_{1}^2)$ and $N(\mu_{2},\sigma_{2}^{2})$. Show that the distribution of $(X,X+Y)$ is bivariate Normal with mean vector $(\mu_{1},\mu_{1}+\mu_{2})$ and covariance matrix</p>
<p>$$ \left( \begin{array}{ccc}
\sigma_{1}^2 & \... | 74,173 |
<p>I am asked to draw a scatterplot and to compute a correlation coefficient for the following situation. A group of subjects are measured for a blood characteristic before and after surgery.</p>
<p>Is it OK to correlate before-and-after data?</p>
<p>I know that it is not OK to perform correlations on non independent... | 36,892 |
<p>Let $f_i(y)$ for $i = 1, \ldots, n$ be valid PDF’s, and let $a_i ∈ (0, 1)$ be constants, such that $\sum_{i=1}^n a_i= 1$.</p>
<ol>
<li>Show that the function $f(y) = \sum_{i=1}^n a_i\, f_i(y)$ is a valid PDF.</li>
<li>If $E [Y_i] = \mu_i$ and $\text{Var}(Y_i) = σ^2_i$, show that<br>
(i) $E[Y] = \sum_{i=1}^n a_i\, \... | 31,273 |
<p>I have a <code>SPSS</code> Output for a logistic regression. This output reports two measure for the model fit, <code>Cox & Snell</code> and <code>Nagelkerke</code>.</p>
<p>So as a rule of thumb, which of these R² measures would you report as the model fit?</p>
<p>Or, which of these fit indices is the one that... | 49,889 |
<p>I'm willing to apply machine learning with <code>R</code> (I will start with random forests then maybe have a look at NNs) on some data, but I don't know where to start, probably because I don't know which words to put on my problem and what to google for.</p>
<p>My data consist in a set of events of type A, each o... | 36,893 |
<p>I came across a paper related to Bayesian decision theory where the absolute loss function is introduced somewhat straightforwardly. This is part of the result.</p>
<p>$\frac{\partial}{\partial a}\int_{-\infty}^a (a-\theta)\! f(\theta|y) \, \mathrm{d}\theta$ = $\int_{-\infty}^a \! f(\theta|y) \, \mathrm{d}\theta$... | 45,212 |
<p>in a one way anova F test
when F=37.45; df1=5; df2=40
what is the P value?
I tried several software, and the result is <0.0001. I know it sounds weird that I need a really small number of possibility. However, I really need it for a publication.
I greatly appreciate if anyone can help on this issue. Please let me... | 36,894 |
<p>I have two separate time series, indexed by time in nanoseconds. They both measure the same thing but because they come about in two completely different ways, the number of observations they each give are not only irregularly spaced but are also different in number and don't align. Even the time is on different clo... | 36,895 |
<p>Let $X_1, X_2...X_n$ be iid with $f(x,\theta)=\dfrac{2x}{\theta^2}$ and $0<x\leq\theta$.
Find $c$ such that $\mathbb{E}(c\hat{\theta})=\theta$ where $\hat{\theta}$ denotes MLE of $\theta$.</p>
<p>What I have tried:
I found the MLE of $f(x;\theta)$ to be $\max\{X_1,X_2\cdots X_n\}$ (which aligns with the answer ... | 74,174 |
<p>Bear with me as I try to word this question well (I'm a mathematical modeler, but not a statistics guru).</p>
<p>We want to assess the response patterns of a binary timeseries. The data are from people answering questions for information they have not previously seen. The scenario is that answers are either correct... | 74,175 |
<p>I work on a website that gets around 150,000 unique visitors a month.</p>
<p>I am proposing to sample one in 1,000 people visiting the site with a pop-up survey as described in this <a href="http://stats.stackexchange.com/questions/39319/bayesian-user-survey-with-a-credible-interval">question and answer about calcu... | 74,176 |
<p>Is anyone aware of good data anonymization software? Or perhaps a package for R that does data anonymization? Obviously not expecting uncrackable anonymization - just want to make it difficult. </p> | 74,177 |
<p>I’m reading a paper and really struggling with one appendix. Basically they derive conditional expectation of a multivariate normal, conditioning on absolute values. </p>
<p>Let
$$\boldsymbol y
=
\begin{bmatrix}
\boldsymbol y_{a}^{\top} \\
\boldsymbol y_{b}^{\top}
\end{bmatrix}
$$</p>
<p>$$\boldsymbol y \sim \... | 74,178 |
<p>Trying to understand the solution given to this homework problem:</p>
<p>Define random variables $X$ and $Y_n$ where $n=1,2\ldots%$ with probability mass functions:</p>
<p>$$
f_X(x)=\begin{cases}
\frac{1}{2} &\mbox{if } x = -1 \\
\frac{1}{2} &\mbox{if } x = 1 \\
0 &\mbox{otherwise}
\end{cases} and\;... | 74,179 |
<p>I have situation in which I compare many genomic regions between two or more cell lines (CL). Each region is covered by n probes measuring the level of methylation (continuous variable). The coverage (value of n = sample size per region, generally varies between 4 and 20) is different for different regions (array pr... | 61 |
<p>I'm trying to fit linear mixed models to 3 different DV (so three models). I understand that REML gives less biased variance estimates. As im more interested in the fixed effects, I use ML for the initial stepwise model reduction based on AIC-values, and use REML to fit my final (reduced) models. </p>
<p>However, i... | 74,180 |
<p>I am building a model with a highly significant interaction. This interaction was one of our main hypotheses. It is clear, however, that the form that the interaction takes does not represent a meaningful change across levels of either variable (one of which is <strong>time</strong>). The interaction is of 2 quad... | 74,181 |
<p>Which components should use for plotting in a PCA analysis? Should it be component 1 versus component 2, or any combination that shows clustering is okay to use?</p>
<p>Also, I have seen that in a few cases the axis labels mention the variance that is shown (e.g. it says "Principal component 1 (Var. 58.09%)"). Does... | 74,182 |
<p>I am wondering if there is a way of calculating the following:</p>
<p>I have a bag with 5 balls numbered from 1 through 5 that are going to be drawn.
Due to different weights, the balls have different probabilities of being drawn:</p>
<p>$P(Ball1) = 0.4$<br>
$P(Ball2) = 0.3$<br>
$P(Ball3) = 0.1$<br>
$P(Ball4) = 0... | 34,224 |
<p>Can anyone suggest where to obtain the results of the 10,000 coin flips (i.e., all 10,000 heads and tails) performed by John Kerrich during WWII?</p> | 34,226 |
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