question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have the following situation:
There are two systems, $s_A$ and $s_B$. For $s_A$ there are two states: $s_A = a,b$. For $s_B$ there are three states: $s_B = 1,2,3$. Now, what I want to do is measure $s_B$, but this is not possible. Instead, I have the option to measure $s_A$, and I know the following three relation... | 72,050 |
<p>I am searching for a way to calculate the $z$-score for a given percentile $p$. I found <a href="http://www.fourmilab.ch/rpkp/experiments/analysis/zCalc.html" rel="nofollow"> this </a> site doing such a calculation. They have given a formula for calculating $P(Z\leq z)$: </p>
<p>$$
\Phi(z) = P(Z \le z) = \int_{-\in... | 15,677 |
<p>It seems like the PACF graph is more informative than an ACF graph. What information does one get from an ACF graph that can not be gleaned from a PACF graph. (ACF = Auto-correlation function, and PACF = partial Autocorrelation). </p> | 33,832 |
<p>In the card game Pitch using 1 deck with 52 cards and 4 people playing and six cards are dealt to each person and I have a partner and I have a King and wish to bid in the suit the King is in using the King as high what is the percentage my opponents have the Ace in the same suit as my King out of their 12 cards? </... | 44,865 |
<p>Is it better to constrain the data to a range, say [0,1], or to force a mean of 0 and sd of 1? Why? Does the type of input data matter (I'll be using both continuous and categorical variables)?</p> | 72,051 |
<p>I have three estimated parameters, $\hat{\beta_0}$,$\hat{\beta_1}$ and $\hat{\beta_2}$, these follow the ordering $\hat{\beta_1}\leq\hat{\beta_0}\leq\hat{\beta_1}$, where these parameters are estimates from a frequentist likelihood function. I know the variance of $\hat{\beta_1}$ and $\hat{\beta_2}$. Can the varianc... | 72,052 |
<p>I am having difficulty in deriving k-means from Mixture of Gaussians. I am following the notation from Bishop (2006), Section 9.3.2: </p>
<p>Suppose we have :
$$
p(\mathbf{x}| \boldsymbol{\mu}_k, \boldsymbol{\Sigma}_k ) = \frac{1}{(2\pi \epsilon )^{1/2}} \exp \left( \frac{ -1 }{ 2 \epsilon } \| \mathbf{x} - \bolds... | 72,053 |
<p>Ok, this is a question that keeps me up at night.</p>
<p><strong>Can the bootstrap procedure be interpreted as approximating some Bayesian procedure (except for the Bayesian bootstrap)?</strong></p>
<p>I really like the Bayesian "interpretation" of statistics which I find nicely coherent and easy to understand. Ho... | 33,836 |
<p>I've done a cross correlation but I'm not sure if what I'm doing is correct...</p>
<p>Here are the command lines I've used so far </p>
<p>(this one is for the first time series. It represents the numbers of subscriptions for men and women on a website during the hours of the day) </p>
<pre><code>data<-read.tab... | 18,578 |
<p>I am trying to do a kselect model from the <code>adehabitatHS</code> which uses commands from <code>ade4</code> package. I am trying to determine if I need to scale my variables. My surface understanding is that the k-select is basically a fancy PCA. In their example they scaled their variables, but their variab... | 15,692 |
<p>While doing some simulations, I realised that the sample quantile is a biased estimator of the true quantile. And, according to my simulations, a potentially <em>very</em> biased one.</p>
<p>I was surprised with that result since the empirical CDF isn't biased, but after some internet research, <a href="http://www.... | 72,054 |
<p>I am trying to determine association between my independent variables (categorical, nominal) and dependent variables (categorical, nominal). </p>
<p>What other statistical analysis I can use aside from chi-square? </p>
<p>Almost all my variables have two levels except two independent variables that had more than 2... | 49,887 |
<p>I am using PCA on foreign exchange return series to find a market "beta". I am using 10 years of daily data with a 2-year half life weighting in the PCA using the package FactoMineR's PCA function. I extract the first principal component return series (so the product of the first eigenvector and the returns matrix) ... | 59 |
<p>As far as I know, one can calculate the relative standard error from the standard deviation of a data sample. I am looking for the Median Absolute Deviation equivalent for standard error. </p>
<p>Does one exist? Also which methods exist to calculate the relative standard error, that do not require the standard devi... | 44,869 |
<p>I am modelling three spatial variables, $v_1, v_2$ and $v_3$ (for example, porosity, water saturation and vshale) that are correlated with each other: $\rho_{12}, \rho_{13}$ and $\rho_{23}$.</p>
<p>Let's say I have generated three uncorrelated Gaussian random fields, UG1, UG2 and UG3, each with their own spatial co... | 15,705 |
<p>I have this data consisting of the variance for different distance, I mean experimental variogram. How can I create a model variogram from this in matlab</p> | 33,844 |
<p>My statistical learning book asserts that when decision trees are constructed, m out of p predictors are randomly selected for consideration in a split. The idea here apparently is to decorrelate trees obtained in bagging by weakening the effect of a strong predictor. If we have p predictors to choose from, and at ... | 33,845 |
<p>I am new to statistics and I am trying to understand the difference between ANOVA and linear regression. I am using R to explore this. I read various articles about why ANOVA and regression are different but still the same and how the can be visualised etc. I think I am pretty there but one bit is still missing.</p>... | 72,055 |
<p>I have the following data of 2 diseases from 5 areas. I want to see if there is any relationship between the 2 diseases.
Incidence Rates of 2 diseases (cases per million per year)</p>
<pre><code> Areas Disease 1 Disease 2
1 4.653 0.751
2 6.910 1.121
3 4.9... | 44,870 |
<p>I have two models with 24 variables in each. I want to see how adding an extra variable (the variable in study) affects the outcome. I used generalised linear mixed models for both models.(GENLINMIXED comman). How do I save the output of the models and compare them? I would like to do what ANOVA in R does. Compare t... | 15,721 |
<p>How can I measure linear correlation of non-normally distributed variables?
Pearson coefficient is not valid for non-normally distributed data, and Spearman's rho does not capture linear correlation.</p>
<p>Thank you</p> | 72,056 |
<p>I am running a GLMM in R using the glmmPQL code from the MASS package. I have been getting a convergence error from the following code.</p>
<pre><code>Calvingglmm2<-glmmPQL(Distance~AllRoads+Natural,random=list(~1|Population,~1|Animal),data=dat,family=Gamma)
summary(Calvingglmm2)
</code></pre>
<p>So I was fiddl... | 72,057 |
<p>I have a certain population U. The members x of U each either satisfy or don't satisfy a property p. That is, p(x) is either true or false for each x in U.</p>
<p>I want to get an estimate of the fraction of members of U that satisfy p. I do this by repeatedly sampling from U (with replacement) for some fixed ti... | 72,058 |
<p>Can you help me to complete the following argument about the identifiability of the random effect $v$ in an additive model. </p>
<p>In an additive model such as $X\beta + v$ the location $v$ is unidentifiable since
$X\beta + v = (X\beta + a) + (v-a)$</p>
<p>Thank you!</p>
<p><strong>EDIT</strong> (following mpikt... | 72,059 |
<p>How can I test the statistical significance of regression coefficients in multivariate multiple regression?</p> | 33,848 |
<p>In case of a multiple linear regression I found a significant effect in a subgroup analysis (sample restricted to males). In the subgroup analysis restricted to females there is no effect. However in a model of the whole sample the interaction term of gender is not significant.
I am aware of the fact that significa... | 44,873 |
<h3>Context</h3>
<p>I have a survey that asks 11 questions about self-efficacy.
Each question has 3 response options (disagree, agree, strongly agree).
Nine questions ask about self-esteem.
I have used a factor analysis of the 11 self-efficacy items and extracted two factors. </p>
<p>$x_1$ to $x_{11}$ denote the 11 ... | 44,874 |
<p>If kNN doesn't perform well for classification on a dataset, is there any hope for parametric methods to perform better? Kernel-based methods, SVM, random forests, and neural networks. Could any of these outperform kNN method?</p> | 72,060 |
<p>I have data from an annual survey which seeks to assess the needs of consumers on a 1 (least important) to 5 (most important) scale. Thus, I have data that looks like so:</p>
<p><img src="http://i.stack.imgur.com/0AKaU.png" alt="enter image description here"></p>
<p>My goal is to assess if the needs of consumers h... | 45,037 |
<p>I use mixed models (random effect for person; repeated measurements) in lme4 to model a continuous outcome. Predictors are both categorical and continous.</p>
<p>My outcome variable (blood pressure; typically between 100 and 170) has a non-linear evolution over time, which is presented in the figure below.</p>
<p>... | 72,061 |
<p>I have a <strong>pretty complex function</strong> that I'm trying to make my computer learn using CNNs. It involves 70 X 70 grayscaled images. The final output is the output of the last unit (it's because I want to predict probabilities from 0 to 1). What's the best layer architecture to address complexity but at th... | 72,062 |
<p>Please check my solution below for estimating Moving Average parameter using the Gauss-Newton (Linearization) method. I consider MA(1).</p>
<p>MA(1) model:</p>
<p>$$z_t=a_t-\theta_1a_{t-1}.$$</p>
<p><strong>Solution:</strong></p>
<p>The residual of this model is,</p>
<p>$$a_t=z_t+\theta_1a_{t-1}.$$
The residual... | 72,063 |
<p>I have a time series and fitted an AR(I)MA object (I really just want an ARMA process so the order is (p,0,q)) in R. Now I'd like to "continue" that process (I guess what I mean is perform simulations). </p>
<p>I found arima.sim() but I'm not sure how to get it to use my existing time series (that I'd like to "cont... | 72,064 |
<p>I am trying to form a model on a set of data that I gathered from MT4. The OHLC and some MA slopes.</p>
<p>I am trying to get the best guess for price change in the future. </p>
<p>I am using</p>
<pre><code># Packages
require(quantmod) #for Lag()
require(nnet)
require(caret)
#Fit model
model <- train(change ~... | 72,065 |
<p>Consider the linear model $y = \mathbf{X}\mathbf{\beta} + \epsilon$.</p>
<p>The residual variance-covariance matrix is given by $\text{Var}(\epsilon)$. </p>
<p>Greene's textbook* states that:</p>
<p>$$Var(\epsilon) = E[Var[\epsilon|\mathbf{X}]] + Var[E[\epsilon|\mathbf{X}]]$$</p>
<p><strong>Why is this the case?... | 33,853 |
<p>I am working on the Chinese economy and my topic of research is how external political instability can affect Chinese exports. So I want to estimate the Chinese export demand function for 1988-2011 with more than 130 countries. I want to estimate the regression equation given below.
$$
\begin{align}
\log(\mathrm{exp... | 45,129 |
<h3>Background</h3>
<p>In sensory science, "replication" means having a panelist in a taste panel do multiple rounds of the same test. You cannot just count those additional rounds as additional panelists, because panelists might show consistent performance. In that case, replications would just confirm the abilities ... | 72,066 |
<p>I intend to run a Binary Logit with Wholesale Price Index of different commodities. I have converted these scale variables into categorical variables with the following criterion: </p>
<p>1=Price has increased when compared to previous period
0=Price has remained stable or decreased in comparison to previous period... | 350 |
<p>One of the main differences between Bayesians and frequentists is that they have a subjective interpretation to probability.</p>
<p>However, do Bayesians actually interpret subjectively the probabilities attached to an outcome GIVEN a set of parameters (i.e. for the likelihood), or is it just that they attach a sub... | 72,067 |
<p>I'm reading about MDL principle and my problem is on a book called: "Guide to intelligent data analysis", 2nd edition page 106.</p>
<p>I have added here a picture of the page I'm having trouble with. Could someone decode what the author is saying in the highlighted area:</p>
<p><img src="http://i.stack.imgur.com/s... | 72,068 |
<p>For example, we always assumed that the data or signal error is a Gaussian distribution? why?</p>
<p>I have asked this question on stackoverflow, the link: <a href="http://stackoverflow.com/questions/12616406/anyone-can-tell-me-why-we-always-use-the-gaussian-distribution-in-machine-learni">http://stackoverflow.com/... | 33,858 |
<p>A dataset has a few attributes. One of the attributes(attribute X) represents a distance with values expressed in meters. I use cross validation to estimate the performance of Decision tree and k nearest neighbor classifiers.
My questions
1) Why will the performance of k-nn change if I change the representation o... | 1,031 |
<p>Let ${\bf X} = (X_1, \dots, X_n)$ denote the log-intensities of all $n = 291$ tropical cyclones from the north Atlantic basin between 1980 and 2006. Log-intensity is defined as the logarithm of its maximum sustained windspeed (measured in knots). A tropical cyclone is a category 5 hurricane if its maximum sustained ... | 44,900 |
<p>I have a question related to linear function estimation. Suppose the potential line function model can be expressed as <code>ax+by+c=0</code>, where <code>a, b, c</code> are the unknown parameters that needed to be estimated. Now a set of data is given <code>(x1,y1), (x2, y2), ... (xn, yn)</code>, and we want to mak... | 72,069 |
<p>As a follow-up to <a href="http://stats.stackexchange.com/questions/41390/test-for-effects-of-two-categorical-variables-on-a-binary-response-variable">this question</a>, I have the following data:</p>
<pre><code> Site Treatment Survival
1 BED DN 1.0
2 BED DN 1.0
3 BED DN ... | 33,860 |
<p>As is known to all, feature engineering is extremely important to machine learning, however I found few materials associated with this area. I participated to several competitions in <a href="http://www.kaggle.com">Kaggle</a> and believe that good features may even be more important than a good classifier in some ca... | 49,037 |
<p>I have a regression problem where the outcomes are not strictly 0, 1 but rather in the range of all real numbers from 0 to 1 included $Y = [ 0, 0.12, 0.31, ..., 1 ]$.</p>
<p>This problem has already been discussed in this <a href="http://stats.stackexchange.com/questions/29038/regression-for-an-outcome-ratio-betwee... | 72,070 |
<p>I am analyzing some stats for a paper I am writing. I have statistics help available through my faculty but am not there for a couple of months so hoping you can help out.</p>
<p>n = 463, 2 patient groups( <70 & >= 70 years). Using SPSS.</p>
<p>I have assessed a whole bunch of stats using Pearson's $\chi^2$... | 72,071 |
<p>Chris Chatfield, whose many quality books and papers I enjoyed reading, in (1) gives the following advice:</p>
<blockquote>
<p>For example, the choice between ARIMA time-series models with low and approximately equal values of the AIC should probably be made, not on which happens to give the minimum A... | 72,072 |
<p>I'm working on the Gompertz growth model to fit weight at age: $$ m(a)=m_{\infty}e^{-\gamma exp(-g{1}a)}$$</p>
<p>Where $m_{\infty}$ and $g_{1}$ are coefficients to be estimated.</p>
<p>To deal with lack of normality I transformed my data using Box&Cox, and to deal with heterogeneity I used weights. After app... | 72,073 |
<p>I used both logistic (binomial distribution) and multinomial regression on a range of different datasets. For simplicity, I only have one explanatory variable in the linear predictor. </p>
<p>I also calculated the confidence bounds for the predicted probabilities, following <a href="http://support.sas.com/documenta... | 33,864 |
<p>Say, for instance, I'm estimating a model with about 5 million observations using linear regression or MLE. Given that the estimates are consistent, using the standard rule of rejecting the null on a 5% significance level will pretty much never make me entitled to reject the null (of the parameter being equal to zer... | 49,627 |
<p>This is more of a "how to use R" question than an actual hardcore statistics question, but I think the concentration of R masters here makes this a good forum for it. I'm refreshing a time series graphing package that currently uses gnuplot. The first step is getting somewhere close to the current graphs, and then I... | 44,919 |
<p>I'm doing survival analysis with time-dependent variables and I have two types of data: birds followed in a biweekly basis and others followed randomly. </p>
<p>I think that analysing both types of data together is a major problem.</p>
<p>Any suggestions in how to deal with it?</p> | 33,866 |
<p>In a Markov chain, a state $j$ is transient if $f_{jj}<1$ ($f_{jj}$ is probability of ever visiting state $j$ starting from state $j$ ).
Suppose, I have an irreducible transient DTMC (means all states are transient). Now, I want to prove that for any $i,j$ in $S$ ($S$ is DTMC state space), $f_{ij}$ (i.e probabili... | 72,074 |
<p>I had a couple of questions about interpreting odds ratios for continuous variables in logistic regression. I feel like these are basic questions about logistic regression (and probably about regression in general), and although I'm slightly ashamed that I don't know the answers, I'm gonna swallow my pride and ask t... | 33,868 |
<p>I had thought that a principal components analysis gives us information about the number of degrees of freedom (i.e. independent variables) underlying a system which we may only be able to observe through derived (and possibly correlated) variables. But a simple experiment has made me doubt this:</p>
<p>I generated... | 15,970 |
<p>How can I interpret point-biserial correlation? If the results give me a positive and significant correlation, how should I interpret it? Should I say that the variable category that I coded 1 is positively correlated with the outcome variable?</p> | 33,870 |
<p><a href="http://stats.stackexchange.com/questions/11256/regression-on-a-non-normal-dependent-variable">Related to my earlier question</a>, I need to perform regression on a skewed dependent variable (n = 500). Since the residuals weren't normally distributed, I was able to transform the DV non-linearly in a way that... | 72,075 |
<p>I need to do a regression with a non-normal DV for which no proper non-linear transformation (that I know of) exists:</p>
<p><img src="http://i.stack.imgur.com/7fPjE.png" alt="enter image description here"></p>
<p>It is a score ranging from 10 to 50, with a high peak at 10, a drop at 11 and a regular decline from ... | 49,428 |
<h3>Context:</h3>
<p>I am analysing some impact assessment data (measuring invertebrate richness in response to pollution), but they are unbalanced - there are not data for every site at sampling occasion, and there were more datapoints recorded <em>after</em> the impact than <em>before</em> the impact. </p>
<p>I am ... | 72,076 |
<p>I've noticed this issue coming up a lot in statistical consulting settings and i was keen to get your thoughts.</p>
<h3>Context</h3>
<p>I often speak to research students that have conducted a study approximately as follows: </p>
<ul>
<li>Observational study</li>
<li>Sample size might be 100, 200, 300, etc.</li>
... | 72,077 |
<p>I received a question today that I wasn't exactly sure how to answer. </p>
<p>I have built a predictive model using a fairly basic logistic regression that works pretty well and fits our business needs. Recently, we purchased a CRM tool that allows us to build "probability" scores, but only allows the end users t... | 72,078 |
<p>If I take a set of measurements and test correlation of variable $A$ vs variable $B$ and get a significant correlation, that makes sense to me. But what if further analysis reveals that of those factors, there is only a significant positive correlation within one group, and that group is over-represented. Is the g... | 72,079 |
<p>I obtained three reduced models from a original full model using </p>
<ul>
<li>forward selection</li>
<li>backward elimination</li>
<li>L1 penalization technique (LASSO)</li>
</ul>
<p>For the models obtained using forward selection/backward elimination, I obtained the cross validated estimate of prediction error ... | 15,987 |
<p>When comparing the performance of two classifiers over a single domain, in the context of a classification problem in machine learning, it is common to use a paired t-test, using the 10 average results from 10x10-fold cross-validation as measurements, where the folds at each iteration are the same for the two classi... | 72,080 |
<p>In <a href="http://www.cancerbiostats.onc.jhmi.edu/Piantadosi_clinicaltrials/">Clinical trials - a methodologic perspective</a>, Steven Piantadosi writes (ch.13, p. 334):</p>
<blockquote>
<p>In Chapter 2, I noted the objections to randomization by Abel and Koch (1997) and Urbach (1993), and indicated the worth of... | 44,923 |
<p>Using a Fligner test to infer about the respect of the assumption of homoscedasticity is not very smart given that the Fligner test tests to the null that there is no difference of variance between the groups. This will wrongly favors small sample size. As it has been said by @Michael Mayer <a href="http://stats.sta... | 12,473 |
<p>Does regression analysis measure cause and effect?</p>
<p>If yes, then how? If no, then what is done? Please describe with an example. </p> | 72,081 |
<p>Should I always <strong>order</strong> the data vector in ascending order before using <code>summary</code> function in R? </p>
<p>Or should I just apply <code>summary</code> function directly on raw data vector?</p> | 33,880 |
<p>Given a sample path from a process supposed to be stationary, I saw the sample autocorrelation function of the sample path is used to estimate the autocorrelation function of the process. But this requires that the stationary process is ergodic. So </p>
<ul>
<li><p>is ergodicity checked on the sample path before e... | 72,082 |
<p>Anyone knows a prior (preferably conjugate) to the
<a href="http://en.wikipedia.org/wiki/Multivariate_P%C3%B3lya_distribution" rel="nofollow">multivariate Polya distribution</a>?</p>
<p>I need it for Gibbs sampling. So if anyone has another idea, I am interested.</p> | 33,881 |
<p>I initially asked this on stack overflow and was referred to this site, so here goes:</p>
<p>I am implementing some unsupervised methods of content-selection/extraction based document summarization and I'm confused about what my textbook calls the "log-likelihood ratio". The book briefly describes it as such:</p>
... | 33,882 |
<p>It seems to me that in literature it is assumed that one knows which features / attributes to choose to characterize an item in clustering.</p>
<p>If I have a database with items which have many attributes, how do I know which attributes to choose for a good clustering? Is there any guideline or literature which de... | 72,083 |
<p>The proportional hazards assumption basically says that the hazard rate does not vary with time. That is, $\text{HR}(t) \equiv \text{HR}$. When can we assume this? What if the hazard ratios at various times are: $2.4, 2.36, 2.27$ and $2.03$? Can we make the proportional hazards assumption? Also we have $$ \log[h(t|... | 72,084 |
<p>Is the best way to find the median survival time from a survival plot just to draw a horizontal line from $p = 0.5$ to the curve and project down to the x-axis?</p> | 72,085 |
<p>I am running a mixed factors ANOVA for a brain imaging study on language processing. The design includes four within-subject factors:</p>
<ol>
<li>complexity: simple/complex;</li>
<li>agreement: correct/number violation/gender violation; </li>
<li>hemisphere: left/right;</li>
<li>region: anterior/posterior; </li>
<... | 33,884 |
<p>I am beginner in forecasting, especially forecasting with R and I am really willing to improve my knowledge. </p>
<p>Recently, I started practicing electricity consumption time series forecasting. </p>
<p>The first barrier I faced is the choice of out of sample data for assessing the forecast accuracy of the forec... | 33,885 |
<p>I have a set of data:
<a href="http://pastebin.com/KHLKD8XB" rel="nofollow">http://pastebin.com/KHLKD8XB</a></p>
<p>which is based on TVC (total viable counts - i.e., numbers of bacteria) from water going into a machine (BM), water taken from the machine (IM) and water taken from a device which is washed in that... | 72,086 |
<p>I have writen code for a Box-Cox transformation (see below). But now I want to do a Yeo-Johnson transformation because <code>datc$plot</code> contains zeros. I tried, but I didn't find a solution.</p>
<pre><code>lambda.fm1 <- boxcox(datc$plot ~ datc$cond.evlot*datc$cond.dl*datc$version),
fa... | 33,886 |
<p>We conducted 2 similar surveys in parallel to a group of health care facilities. One was sent to managers, one to staff. Some questions were identical, others asked about different areas of the facility. We received responses from groups of facilities that do not completely overlap. So our response rates were the f... | 72,087 |
<p>There are many algorithms for finding $k$ in the $k$-means algorithm that depend on finding the "kink" in a graph of the objective function. What if I know that the data have either $2$ or $3$ clusters? How do I find which $k$ is "better"? Of course, a higher $k$ will lower the objective function, but this in not ne... | 72,088 |
<p>I would like to know if there are any evaluation frameworks of recommender systems which are capable of evaluating rating prediction and topN recommendation (Precision and recall etc.). Maybe I need to find them in recommender frameworks? If so are they easy to plug in? </p>
<p>As a matter of fact I am working on d... | 72,089 |
<p>I'm trying to learn a bit of statistics, and I thought I'd ask you guys about conducting surveys.</p>
<p>Let's say I conduct a survey like the following <a href="https://docs.google.com/forms/d/1YrqcWQNl1CmbINaVZuL18ZseqBSWemdHjy_P4ES637A/viewform" rel="nofollow">https://docs.google.com/forms/d/1YrqcWQNl1CmbINaVZuL... | 72,090 |
<p>I've been working my way through Vapnik's 1998 <em>Statistical Learning Theory</em> book and one thing that I'm still unsure of is if his risk bounds hold for nonconvex loss functions -- i.e., when we can't be sure we've minimized the empirical risk.</p>
<p>Does anyone know of any references that discuss this?</p> | 31,725 |
<p>I have situation in which I query different sites on the genome (biologically independent) and for each site I get a measurement. I have a number of measurements that are close together on the genome and I call that a region. I then want to compare the measurements of a region between two biological specimens using ... | 72,091 |
<p>I ran the same SEM model in <em>sem</em> and <em>lavaan</em>. I got the same parameters and - generally - very close test values, with the exception of AIC and BIC which were immensely different between the two packages.</p>
<p>The following is the resulting AIC and BIC from <em>sem</em>:</p>
<pre><code>AIC = 291... | 33,890 |
<p>I first noticed this when I was running some models is Stata and the variables that I had used as controls in the second stage were showing up in the first stage (I think this is just Stata's default approach). A lot of these variables are in no way related to the dependent variable in the first stage. Similarly, th... | 72,092 |
<p>I am using <code>mice</code> in <code>R</code>, a chained equations (sequential regression) algorithm, to impute a series of polytomous variables (e.g. scales from 1 to 5 or 1 to 3). Ultimately, my interest is in estimating statistics on simple proportions of categories on these variables (e.g. 1 and 2 versus other)... | 72,093 |
<p>Should my effect size be positive or negative when the control group gains more weight than the experimental group (when it is hypothesised that the experimental group would lose more weight i.e., the difference between groups is due to more weight gain in the control rather than weight loss int the experimental gro... | 33,896 |
<p>I am not a statistics expert and would like to check the validity of a test I hav used on a survey results.</p>
<p><strong>Survey Results</strong>
I asked people (n=264) to characterize a panoramic road they chose in 24 different categories. Each of them could choose as many categories he/she desired. Than I counte... | 72,094 |
<p>I have compiled a very small set of summary data from the literature, and I wish to compare the variances between aspects of the literature-based data, and to some of my own data. The summary data includes the mean, standard deviation and sample size.</p>
<p>In earlier tests, I compared the variances of one continu... | 72,095 |
<p>I found that often in literature that likelihood values are often used to compare different estimation method for the same model. And I got the impression that is the only way likelihood values are used. </p>
<p>However, I wonder what else we can say about the likelihood function. For example, can we compare two t... | 72,096 |
<p>I am hoping someone can help with this - perhaps trivial question of interpreting the formula below. It is the mean residual lifetime (restricted to the window of data) for the case of discrete time.</p>
<h3>Restricted Mean Residual Life</h3>
<blockquote>
<p>Remaining time until event or upper bound--whichever c... | 72,097 |
<p>I'm trying to model clicks in a Google AdWords campaigns. This is a function of impressions, the probability of a click (CTR) on that impression, the cost per click (CPC), and the budget of the advertiser. It's essentially </p>
<p>$$\text{clicks} = \text{impressions} \times \text{CTR}$$ </p>
<p>subject to </p>
... | 72,098 |
<p>How can I understand the label-bias problem in Hidden Markov Models? And why is CRF able to solve this problem?</p> | 33,899 |
<p>Somebody mentioned, I don't remember who, that "there are many ways to specify the prior, you could even draw it!". It is clear to me that it is possible to actually draw the density of the prior using pen and paper and transform it into a histogram prior for use in an analysis. What I'm wondering is:</p>
<p><stron... | 72,099 |
<p>I was reading this paper <a href="http://www.umiacs.umd.edu/~jags/pdfs/KSforNLP.pdf" rel="nofollow">http://www.umiacs.umd.edu/~jags/pdfs/KSforNLP.pdf</a> where they say that</p>
<p>$trace(K \pi^{T} L \pi)$ is a convex function of $\pi$ where $\pi$ is a permutation matrix and K and L are kernel matrices. I am not su... | 33,900 |
<p>I have a dataset with about 6000 obs. in a cross sectional times series structure (countries and years). My dependent/response variable is binary and my independent/explanatory variables are a mix of binary and continuous.</p>
<p>Now, I worry that the explanatory variable I'm interested in might not be independent ... | 72,100 |
<p>I am a biologist looking for guidance regarding which statistical test to use when comparing variances in data. </p>
<p>I am comparing two theoretical distributions to the experimental data. The data in the distributions may not be normally distributed and there may not be an equal number data points. An example of... | 72,101 |
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