question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am trying to estimate parameters of a two dimensional Normal distribution using Gibbs sampling. While it was very easy transform the posterior equation for mean vector to a single dimension normal function for sampling, I am not able to same for sigma(covariance).</p>
<p>Do I need to use the Wishart distribution ... | 47,934 |
<p>This question might be too naive, but I need to understand this point. Suppose I ran a survey for a product for 1000 individuals & collected the data for various aspects of it. Let's say the categories are X1, X2, X3, X4, X5 and X6.</p>
<p>So, now I have 6 variables. I want to know the type of the distribution ... | 37,452 |
<p>I found that learning how MCMC and HMM work went best by writing the code of simple examples myself. I would now like to learn how <strong>random forests</strong> work, but it's again not that trivial to transform the theoretical texts and pseudocode to real scripts (well... for me at least).</p>
<p>Could anybody ... | 73,842 |
<p>I have a time series $X_t$ (shown below) with a structure break. The stationary test <code>kpss.test()</code> says it has a unit root. How to explain this? Why does $X_t$ have a unit root? Sure it is not constant in mean, so it is non-stationary. But I can not relate its non-stationarity to the concept of unit-root.... | 73,843 |
<p>I am looking for resources (tutorials, textbooks, webcast, etc) to learn about Markov Chain and HMMs. My background is as a biologist, and I'm currently involved in a bioinformatics-related project. </p>
<p>Also, what are the necessary mathematical background I need to have a sufficient understanding of Markov mode... | 37,965 |
<p>I have a pretty large data set (~300 cases with ~40 continuous attributes, binary labeled) which I used to create several alternative predictive models. To do this, the set was divided to training and validation subsets (~60:40% respectively). </p>
<p>I have noticed that there are several samples (both in the train... | 36,360 |
<p>Suppose you had $200 US to build a (very) small library of statistics books. What would your choices be? You may assume free shipping from Amazon, and any freely available texts from the internet are fair game, but assume a 5 cent charge per page to print.</p>
<p>(I was inspired by a mailing from Dover books, but m... | 73,844 |
<p>I know that this is probably a question that's been asked plenty of times, but i haven't seen an answer that's both accurate and simple. How do you estimate the appropriate forecast model for a time series by visual inspection of the ACF and PACF plots? Which one, ACF or PACF, tells the AR or the MA (or do they both... | 73,845 |
<p>Consider two simple linear models. </p>
<p>$y_{1j}=\alpha _1+\beta_{1}x_{1j}+\epsilon_{1j}$ and<br>
$y_{2j}=\alpha _2+\beta_{2}x_{2j}+\epsilon_{2j}$ , $ j=1,2,...,n>2$ where $ \epsilon_{ij}$~$N(0,\sigma^2)$<br>
I have two questions.</p>
<p>1 ) Show that the point on the x-axis where the two lines intersect is... | 36,366 |
<p>I am asking for your help because I'm not sure whether the procedure I'm using is correct. </p>
<p>I have two models, M1 and M2, and for each of them I have ten instances (ensemble members). For each model I calculate the output mean of all the members inside the ensemble. Then I compute the correlation between thi... | 73,846 |
<p>The data is measured in two biological replicates with two technical replicates, each. </p>
<ul>
<li>Each variable might be detected only in one or more replicates, in the others it is considered missing at random. </li>
<li>Each variable is measured with zero (missing) to dozens of data points in each experiment.<... | 73,847 |
<p>This is a pretty simple question but I haven't been able to find a clear answer to it. I have some data from a behavioral experiment taken under two conditions (A and B); within each condition, each trial could have one of two outcomes (correct or error). Moreover I repeated the experiment on many subjects.</p>
<p>... | 73,848 |
<p>In a two sided test, assume the test statistic has been chosen to be $T(X)$ and the distribution of $T(X)$ under null hypothesis is also known to be $F$. Let the significance level be $\alpha$.</p>
<p>I can come up with two different ways to determine the rejection region:</p>
<ol>
<li><p>$\{|T(x) - \mu| > c\}$... | 36,372 |
<p>I am composing a regression tree to determine corporate dividends with dividends as the determinant and 13 predictor variables. To check the accuracy of the tree I am using RMSE values computed using a random sample set. The problem is my RMSE values are <strong>huge</strong> since the range of dividends (the determ... | 47,948 |
<p>I have to compute the LCL95% and UCL95% using Land's "exact" method. I computed the LCL and UCL for this lognormal distribution using another technique and I cant find anything for Land's Exact procedure.</p>
<p><code>My data set x = {0.043, 0.236, 0.057, 0.016}</code></p>
<p>here is what i tried</p>
<p>y = mean ... | 73,849 |
<p>What is the relationship between (first) principal component(s) and the correlation matrix or the average correlation of the data. For example, in an empirical application I observe that the average correlation is almost the same as the ratio of the variance of the first principal component (first eigenvalue) to the... | 73,850 |
<p>I am doing a research validating a new questionnaire, which has 156 items divided up in 12 scales. I have run a factor analysis at scale level, which gives me two nice constructs (consistent with theory).</p>
<p>My tutor however is insisting this is no good as according to her I need to run an exploratory factor an... | 73,851 |
<p>I'm wondering how to interpret the coefficient standard errors of a regression when using the display function in R.</p>
<p>For example in the following output:</p>
<pre><code>lm(formula = y ~ x1 + x2, data = sub.pyth)
coef.est coef.se
(Intercept) 1.32 0.39
x1 0.51 0.05
x2 0... | 73,852 |
<p>I have data on two processes, where the process assigns elements into ordered bins. I am interested in testing for agreement between the processes. What is the best way to do this (R code)? Here is the dummy data with counts for the 2 processes and 4 categories). I am not familiar with weighted kappa (which I have s... | 73,853 |
<p>I have four letters: A B C D, I need to calculate all the combinations on the follow type:</p>
<pre><code>A - B
A - C
A - D
A - BC
A - BD
A - CD
A - BCD
AB - C
AB - CD
AB - D
ABC - D
</code></pre>
<p>As you can see no letters are repeated LEFT - RIGHT, IF the letter is on the left it is not repeated on the right... | 38,150 |
<p>I have used 20 variables to extract 4 factors in a factor analysis. Now I want to use the extracted factors (factor scores) as IVs on an outcome variable. Besides I want to include 4 other variables as IVs in the regression which were not used in the factor analysis. That means I want to regress 4 factors and 4 vari... | 47,955 |
<p>I suspect that a series of observed sequences are a Markov chain...</p>
<p>$$X=\left(\begin{array}{c c c c c c c}
A& C& D&D & B & A &C\\
B& A& A&C & A&D &A\\
\vdots&\vdots&\vdots&\vdots&\vdots&\vdots&\vdots\\
B& C& A&D & A &... | 73,854 |
<p>If i want to be Data Scientist in future,
can somebody advise me <strong>sites/books/courses</strong> and other good things to learn?</p>
<p>Thanks!</p>
<p>P.S: i know statistical analysis and R/Matlab/Excel/SAS on different levels, but want to rise my skills in it.</p> | 73,855 |
<p>Given a couple of measurements I get by running an experiment, I need to express the fact that they are similar to some extent. So, I computed their coefficient of variation, i.e., stdev/mean.</p>
<p>Here is a sample:</p>
<pre><code>3.76025 2.98375 3.78946 3.72195 3.11426 3.60366
</code></pre>
<p>and CV = 10.12%<... | 36,378 |
<p>This is a long-winded question but I'll try to paint the picture. I'm using structural equation modeling using Amos software to study relationships between brain and behaviour. I have three condition types - 1, 2, 3 (for simplicity). Within each condition, I have 2 variables that are bidirectionally connected. the v... | 31,163 |
<p>I have a data set of 11,000+ distinct items, each of which was classified on a nominal scale by at least 3 different raters on Amazon's <a href="http://mturk.com" rel="nofollow">Mechanical Turk</a>. </p>
<p>88 different raters provided judgments for the task, and no one rater completed more about 800 judgments. Mos... | 37,611 |
<p>I am using the <a href="http://cran.r-project.org/web/packages/np/index.html" rel="nofollow">np</a> package in R with the <code>npregiv</code> command. The program is in beta, and I cannot call ordered(var) on one of my instruments (a bug in the program I am pretty sure, the help file says this is allowed). The va... | 73,856 |
<p>Goal: I want to visually depict the difference between experimental treatments while controlling for a continuous covariate in Poisson regression.</p>
<p>In my experiment, I am seeking to explain the number of species of insect on plants (richness) with a 3-level treatment factor and the size of the plant as a cont... | 36,380 |
<p>If $x$ and $y$ are two series, is there any relation between $\sum{(x,y)}$ that can be expressed in terms of mean of these two. Specifically, I want to know if any sort of relation exists between $\sum(x,y)$ and $\sum{(\bar{x}, \bar{y})}$.</p> | 73,857 |
<p>I have four nested models.Every of them learned from different data sets. now I want to compare these models together.normally people try to compute the F-satistics. But for my case, it's bit harder, because each of these modeles comes from diffrent data.
Does someone have idea how can I compare modeles together in ... | 73,858 |
<p>Let $X,A,B,C,D$ be time-series variables and the covariance between any two pairs of these are known.</p>
<p>Suppose we want to find $\textrm{cov}(X,aA + bB + cC + dD)$, where $a,b,c,d$ are constants.</p>
<p>Is there any way of doing this without expanding out $E[(X-E[X])(aA+......)]$? </p> | 36,383 |
<p>Is there any way to estimate the bias of the estimate of the betas in a linear regression model when the actual beta values are unknown?</p>
<p>The well known Mean Square Error (MSE) criterion is used to quantify the performance of different biased estimators but to calculate the bias you need to know what the corr... | 36,385 |
<p>A jar has 50 balls 1 to 50 each one having distinct number written on it. Bob, owner of the jar,each day he takes out one ball out of the jar randomly ( with equal probability) and put it back.</p>
<p>Q1. How many days on average will it take until all 50 balls are taken out? (Note that the same ball can be picked... | 19,031 |
<p>I have a feature x, that I use to predict a probability y.</p>
<hr>
<p><strong>Some background on (x,y)</strong></p>
<p>I can't go into too much details, but hopefully the following should be enough to explain what x and y are, at least conceptually <em>[square and circles are NOT the actual label I am working wi... | 73,859 |
<p>I am an epidemiologist trying to understand GEEs in order to properly analyze a cohort study (using Poisson regression with a log link, to estimate Relative Risk). I have a few questions about the "working correlation" that I would like someone more knowledgable to clarify:</p>
<p>(1) If I have repeated measurement... | 73,860 |
<p>I am trying to fit to a long series of data about tide to a sinusoid function. I would like to have on the y axis the height of the tide (from $-$2 m to 5 m) and on the x axis the time in hours 24h.I do not know how to do it. I want to fit a sine wave, and my period is actually every six hours, when the tide changes... | 73,861 |
<p>I had trouble coming up with a title, so hopefully I can explain it better here.</p>
<p>I'm working on a classification problem and I'm doing some pre-analysis of variables. I'm looking for some nice ways to visualise the distribution of the target variable within each independent variable.</p>
<p>As an example fo... | 73,862 |
<p>My experiment is a completely randomized block design. The objective is to find whether a variable is different between species $a$, $b$, $c$. The measurement was taken 2 times (June, July) in each year (2011, 2012). I was wondering whether repeated measures ANOVA is a correct method to use? If it is, would you ple... | 47,966 |
<p>I have a small pilot dataset containing experimental measurements for 12 samples, 4 numeric predictors and 1 numeric outcome variable. The goal is to obtain a first rough estimate on the extent to which the outcome variable can be predicted using one or more of the 4 predictors, before deciding on whether it's worth... | 73,863 |
<p>I have some questions regarding the usage of CATPCA in SPSS. I hope the answers to these questions will be helpful for others too who are planning to work on it.</p>
<p>1) In my <a href="http://www.4shared.com/file/U0kF2JRK/4factoranalysis.htm" rel="nofollow">data</a> (on this data I want to run a CATPCA), there ar... | 73,864 |
<p>Does this probability distribution have a name?</p>
<p>$$f_a(x) dx = \frac{a}{e^a-(a+1)} \left(e^{a x} - 1\right) dx, \quad 0 \le x \le 1.$$</p>
<p>Edit:
I want $a$ to be positive. I don't think this is what is usually called a truncated exponential distribution.</p>
<p>Edit 2:
Here's an
<a href="http://www.wolf... | 73,865 |
<p>I have a multi-class short text classification task with a minor wrinkle: I'd like to also detect when the texts don't fit any of the classes well. I've tried to do it by simply adding unrelated texts into a separate class and learning an SVM, but with little success so far. Unsurprisingly, since 1) there are very m... | 73,866 |
<p>After attempting to produce a linear mixed model, I was left with a great deal of heterogeneity.</p>
<pre><code>lme1 <- lme(Average.payoff ~ Game + Type + Others.Type + Game:Type +
Game:Others.Type + Type:Others.Type, random=~1|Subjects, method="REML",
data=Subjectsm1)
</code></pre>
<p>The response term <... | 113 |
<p>I want to use Hidden Markov Models for an unsupervised sequence tagging problem. Due to the peculiarities of my application domain (recognition of dialogue acts in conversations), I would like to use multiple emissions for each state (that is, multiple features). Graphically, the model would therefore look like this... | 36,396 |
<p>Can somebody point me in the right direction for a treatment of the following problem? I imagine this should be a fairly common problem in medical statistics...</p>
<p>Given two binomial random variables $X_1\sim Bin(n_1,\pi_1)$ and $X_2\sim Bin(n_2,\pi_2)$ I am looking for the posterior distribution of $\pi_1-\pi_... | 73,867 |
<p>I often use the instance weights with Libsvm for classification problems.
<a href="http://www.csie.ntu.edu.tw/~cjlin/libsvmtools/#weights_for_data_instances" rel="nofollow">http://www.csie.ntu.edu.tw/~cjlin/libsvmtools/#weights_for_data_instances</a></p>
<p>Does anyone know the details of the algorithm that is imp... | 73,868 |
<p>I have a time series (shown below) that comes from a sensor whose calibration was changed in the middle of last year. As part of this change, the sensor's reading of the variance (or volatility) of the observations increased, although actually, this volatility did occur before the change in calibration, but it was ... | 36,399 |
<p>I'm working with bird songs. A song is composed of many vocal parameters [highest frequency (Hz), lower frequency(Hz), bandwidth(Hz), duration (s), number of notes, and son on....]</p>
<p><strong>I'm interested in exploring the relationship between geographical distance and bird songs, to see if some pattern of var... | 73,869 |
<p>The probability that a certain radioactive mass emits no particles in a one-minute time period is 0.1353. What is the mean number of particles emitted per minute?</p>
<p>From the above I was able to deduce that P(X>=1) is 1 - 0.1353 = 0.8647.</p>
<p>0.8647 chance of at least 1 particle being emitted in a minute.</... | 73,870 |
<p>What motivates, justifies, gives rise to the differences between the Gumbel, Fréchet, and Weibull distributions? Glen_b's comment indicates that they are distributions for extreme values generated by different kinds of distributions in IID sequences. What are those different kinds? [EDITed in response to Glen_b's ... | 73,871 |
<p>Background: I'm giving a presentation to colleagues at work on hypothesis testing, and understand most of it fine but there's one aspect that I'm tying myself up in knots trying to understand as well as explain it to others.</p>
<p>This is what I think I know (please correct if wrong!)</p>
<ul>
<li>Statistics that... | 73,872 |
<p>I am trying to figure out if value-at-risk (VaR, a quantile) type tests could capture if expected shortfall (expectations above a quantile) point forecast generated from a type of model could be regarded as accurate or not. </p>
<p>I base my curiosity from this quote from <a href="http://www.bis.org/publ/bcbs_wp19.... | 73,873 |
<p>I am looking for a research paper that basically describes a hidden markov model that has multiple observations, and some observations that have conditional dependencies. For example, please consider the following figure that shows two latent states with 5 observed variables. Here the variable obs5 is dependent on i... | 16,691 |
<p>I have a nested model with the following effects</p>
<ul>
<li>fixed: treatments</li>
<li>random: experiment_date</li>
</ul>
<p>I used <code>lme()</code> to model the data</p>
<pre><code>mod1 <- lme(N_cells ~treatments-1, random=~1|experiment_date, method='ML')
</code></pre>
<p>Then I want to compare all the o... | 73,874 |
<p>I have a naive Bayes classifier with two classes (target and non-target) and distributions for a number of features (the same for both classes). </p>
<p>I know that some features contribute more, or less to the overall classification accuracy.
I can use KL-divergence to measure the information gain from feature di... | 36,404 |
<p>I have a nested repeated measures question. I have 20 individuals grouped into 5 families. For each individual I have measurements on subsequent days pre, during, and post-treatment for a total of 6 measurements per individual (on days 1 and 2 pre-treatment, on days 4 and 5 during treatment, and days 7 and 8 post-... | 73,875 |
<p>I have a question. </p>
<blockquote>
<p>In a two sample t test, a confidence interval for $\mu_2-\mu_1$ is constructed based on the hypothesis test $H_0: \mu = \mu_0$ versus $H_{a}: \mu \neq \mu_0$? </p>
</blockquote> | 73,876 |
<p>I have used Mixture Density Networks for probability density function prediction. I am wondering how I can calculate Root Mean Square Error (RMSE) of predicted pdf in MATLAB.</p>
<p>Thanks.</p> | 36,406 |
<p>i was asked to describe a non-trivial data (n not equal to =/1) example where the leverages would all be equal for QR decomposition question. could someone help?</p> | 31,272 |
<p>I have a series of measurements in which something is sampled and placed into either category 1 or category 2. I have 3x2x3 factors for each set of measurements, and each set of measurements is done independently 3 times. </p>
<p>What is a good statistical test to look examine the combined effects of each factor,... | 73,877 |
<p>I was running some timing simulations on a computer. As is often done with low latency things like this, I was running the relevant block in a loop $k$ times and then recording the total time over $k$ (average time). I repeated this thing $100$ times for $k=10000$ and $k=100000$ respectively and computed a mean and ... | 47,979 |
<p>I am trying to understand what the reported intercept is showing when I use <code>arima()</code> with <code>xreg=</code>. The documentation says</p>
<p>"If am xreg term is included, a linear regression (with a constant term if include.mean is true and there is no differencing) is fitted with an ARMA model for the e... | 73,878 |
<p>I have read this link.</p>
<p><a href="http://stats.stackexchange.com/questions/3730/pearsons-or-spearmans-correlation-with-non-normal-data">Pearson's or Spearman's correlation with non-normal data</a></p>
<p>I cannot comment on the original post. Therefore I ask here:</p>
<p>I have two variables are <str... | 73,879 |
<p>I would like to perform an individual-level multivariate analysis at small levels of geographic aggregation (Australian census collection districts). Clearly, the census isn't available at these small levels of aggregation for privacy reasons so I am investigating other alternatives. Almost all the variables of in... | 47,981 |
<p>Here is my example. Supose we evaluate a characteristic using two different methods (a and b) and we want to study if both methods performs in a same way. We also know that these two measures have been recorded from two different groups, and the mean values for each one of these groups are highly different. Our data... | 36,411 |
<h3>Context</h3>
<p>I have two sets of data that I want to compare. Each data element in both sets is a vector containing 22 angles (all between $-\pi$ and $\pi$). The angles relate to a given human pose configuration, so a pose is defined by 22 joint angles.</p>
<p>What I am ultimately trying to do is determine the ... | 73,880 |
<p><a href="http://www.biomedcentral.com/1471-2105/10/318" rel="nofollow">Kavosh</a> is a recent package designed for <a href="http://en.wikipedia.org/wiki/Network_motif" rel="nofollow">network motif</a> discovery. To give a comparison, Kavosh generates a collection of similar networks using an MCMC process.</p>
<p>T... | 36,412 |
<p>I have been using $r = \mu \ln(1 - n)$ to obtain pseudo-random numbers from an exponential distribution, where $\mu$ is the distribution mean and $n$ is a pseudo-random number from 0 to 1. Now I want to do the same thing, but use a distribution that has a scale parameter. Can I simply scale the result of the above... | 31,503 |
<p>i use e1071 package in R for SVM regression prediction and tried the same test in C# libsvm and got different results. All the parameters (gamma,cost,eps) are the same and so is the scaling method. The predictions differences average is about 0.015 (850 test samples). Is that a reasonable difference? What may be the... | 73,881 |
<p>I am learning about ridge regression, so I am implementing it in MATLAB as practice. However, I am having trouble finding a structure of data where ridge regression performs better than an ordinary least squares.</p>
<p>Reading up I've found that data that is collinear is often better to be regularized. However whe... | 73,882 |
<p><a href="http://www.cs.toronto.edu/~hinton/adi/index.htm" rel="nofollow" title="DBN Generation Demo">This demo</a> shows the DBNs capability to associate different input modalities ("images of digits" and "labels").</p>
<p>By clamping one modality at the top layer, the network can infer the other via (Gibbs) sampli... | 36,416 |
<p>I could really use a hit as to which statistical test I need to use to address the following problem:</p>
<p>I have three different species: A, B and C.
I have compared the quantitative overlap of Species A and B, respectively, with that of 'Species C' (using a Fisher's test for each of the two cross-species compar... | 36,418 |
<p>I have a regression problem with 5-6k variables. I divide my data into 3 non-overlapping sets: training, validation, and testing. I train using only the training set, and generate a lot of different linear regression models by choosing a different set of 200 variables for each model (I try about 100k such subsets). ... | 73,883 |
<p>This is actually part of a problem from <em>All of Statistics</em>:</p>
<p>$X_1, X_2, \ldots, X_n \sim \text{Uniform}(0, \Theta)$. And $Y = \text{Max}\{X_1,\ldots, X_n\}$.</p>
<p>If you're given that $Y > c$, can you estimate the probability of $\Theta>1/2$?</p>
<p>Of course if $c\ge1/2$ the probability is... | 6,866 |
<p>I have been thoroughly confused by a bunch of online resources regarding this issue. I would really like a simple explanation about the differences between generative and discriminative approaches, and where "discriminant functions" figure in all this. I would especially appreciate any explanation or a pointer towar... | 36,421 |
<p>We've got a 524*40 data frame of responses to a likert-type scale questionnaire (7 response categories on 40 items). We want to do exploratory multidimensional IRT using the MHRM method to identify the latent structure. When we run </p>
<pre><code>mirt(SAQdata3, 4, method = 'MHRM')
</code></pre>
<p>we get the foll... | 73,884 |
<p>My panel regression model is as follows:
$$Y_{it}=PS_{it}+PF_{it}+EF_{it}+ \mathbf X_{it}+e_{it}$$
where </p>
<ul>
<li><p>$i$ : country, </p></li>
<li><p>$t$ : year, </p></li>
<li><p>$Y_{it}$ : GDP per capita, </p></li>
<li><p>$PS_{it}$ : Political stability, </p></li>
<li><p>$PF_{it}$ : Political Freedom, </p></l... | 73,885 |
<p><strong>Hello</strong>,</p>
<p>first of all I've got to confess that I'm not a statistician and therefore wouldn't mind if an answer is a bit more explicit than it usually would be among statisticians.</p>
<h2>The Context</h2>
<p>To predict energies of arbitrary patterns of a certain physical system, I settled to... | 73,886 |
<p>How do you calculate (1.4) below?</p>
<p>From "Distribution of Residual Autocorrelations in Autoregressive-Integrated-Moving Average Time Series Models" (Box and Pierce 1970):</p>
<p><img src="http://i.stack.imgur.com/ui1hB.jpg" alt="enter image description here"></p>
<p><a href="http://www.jstor.org/stable/22843... | 73,887 |
<p>I've have a variable that has a regression coefficient of 5 using OLS, but when I use quantile regression (examining every 5th percentile, 5, 10, 15, etc.), I find a coefficient that is anywhere from 1/100th to 1/5th of the size of the OLS coefficient. It never really approaches the OLS coefficient. What is causing ... | 31,423 |
<p>I have used scaling on features of a model which contains 40 features (all columns are numbers) and a binary output variable. </p>
<p>This is the Kaggle contest <a href="http://www.kaggle.com/c/data-science-london-scikit-learn" rel="nofollow">here</a> I've scaled the features assuming it would deliver better perfor... | 73,888 |
<p>I have to determine periodicity of the states of the chain and I think that the chain is aperiodic but I don't know how to argument it. Is it correct and mabye there is some calculation that I can do to prove it? I also think that state one can have a period 2 because it can be visited only at the multiple of two mo... | 73,889 |
<p>Given the joint density $f_{12}(x_1,x_2)$ of two (dependent) random variables $X_1$ and $X_2$, each defined on $\mathbb{R}$. Suppose that $f_{12}$ is differentiable everywhere on $\mathbb{R}^2$. Now define the event </p>
<p>$Y=\{(x_1,x_2) : x_2 - x_1 \leq d\}$ </p>
<p>for some real $d$. </p>
<blockquote>
<p>W... | 73,890 |
<p>I am having a little trouble understanding the concept and derivation of the likelihood of truncated data.</p>
<p>For example, if I want to find the likelihood function based on a sample from a distribution, but when taking a sample from the distribution, I observe the truncated values (where there is a cut-off of ... | 36,430 |
<p>I would like to implement (in R) an instrumental variable (IV) estimator, that takes the most general form (here not 2SLS or GMM!):
$$ \beta_{IV} = (Z'X)^{-1}Z'Y $$</p>
<p>I could code this in the naive way, inverting $Z'X$, and computing the rest, but I remember that this is very inefficient in term of computing, ... | 73,891 |
<p>I have an item for which I slowly collect rating values on a website. It is a movie item on a website and at the beginning it has no rating but I assign it a Gaussian prior $N(\mu_0, \sigma_0^2)$. A person comes on the website and gives it 4 out of 5 (note that I have only discrete ratings 1, 2, 3, 4 and 5 stars) </... | 73,892 |
<p>I am coding a questionnaire on STATA and there is a question about Father Education with the option "Don't know" at the end. I am not sure how to code it, because I don't want to count it as missing variable, since the students that answer the questionnaire might have been raised by single moms, etc, and the "don't ... | 48,023 |
<p>I have a model with variables (financial ratios) and some of them are in percentages, some in days and some just ratios (negative and positive). I ran an ANOVA and the results were not so good. When I applied the Shapiro test, 24 out of the 26 variables were not normally distributed. So I log-transformed every varia... | 38,154 |
<p>I have conducted a repeated measures ANOVA, with 2 factors: </p>
<ul>
<li>One between factor (<code>Ex_control</code>: exercise intervention versus control) </li>
<li>One within factor (<code>time</code>: pre/post intervention). </li>
</ul>
<h3>Questions</h3>
<ul>
<li>Should I first refer to the table labelled <c... | 1,025 |
<p>Let's say I fit an ARIMA model on a time series up to date t.</p>
<p>I want to forecast the 10 next values without refitting the model but also using the latest data available for each date.</p>
<p>So
forecast for (t+1) uses the model fitted from 1 to t and the time serie from 1 to t</p>
<p>forecast for (t+2) use... | 73,893 |
<p>Disclaimer: I understand that this question is specific to the types of data, the end goal, etc. but I just wanted to get some quick tips regarding calculating dissimilarity between different types of data. This/clustering is probably the area of ML in which I am least comfortable.</p>
<p>Let's say I have a dataset... | 73,894 |
<p>I saw a famous review paper about intelligence, and the authors introduced a way to adjust the regression coefficient for predictor error.</p>
<p>As many of you might know, if the predictor has a measurement error or if it has reliability less than 1, the regression coefficient estimate(OLS) is biased towards 0.(le... | 36,439 |
<p>I want to plot a ROC for my detection algorithm which is used to detect features
in image. I had obtained true positive, false positive and false negative from
the algorithm. There is no true negative in my case. </p>
<pre><code> I had run the algorithm for 6 images so i got 6 number of TP,FP and FN. With
</code... | 73,895 |
<p>If time series is tested for Unit Root, (by ADF, PP, KPSS,...) problem is detected with some tests and not found by others. which one is preferred? For example if ADF says us that Unit root is existed and PP says that is not problem, Which one of them would be preferred?</p> | 73,896 |
<p>I have some trouble interpreting R's <em>RandomForest</em> variable importance measures when using multiple polytomous dummy variables. </p>
<p>Take the following example: I have paired country data, e.g. representing two different parties in conflict ("attacker" and "defender"), with each party representing one of... | 73,897 |
<p>Can one please refer me to a formalism and optimization algorithms of SVM which outputs not only 0/1 but a vector of 0/1's, i.e. I'd like to train multiple classifiers at once for the same input.</p>
<p>Thanks!</p> | 36,443 |
<p>I have a model where time is the response variable. I'd like to generate confidence intervals for the estimates. I have established that the error in the estimation is roughly normally distributed (it may be more cauchy). The Mean and Median are very different, with the median more accurately representing the middle... | 73,898 |
<p>I have monthly sales data of 500 restaurants for one year. </p>
<p>For the same restaurants, I also have customer defection or dissatisfaction rates. </p>
<p>I want to create a composite score that can rank restaurants based on their performance on sales and customer satisfaction. Something similar to customer lif... | 73,899 |
<p>Given a classifier (SVM) classifying in 2 'classes' (+1 or -1) for prediction purposes. It has an AUC score of 0.28, meaning its success rate is lower than just random predictions.</p>
<p>If I just do the opposite (ie: classifier says it'll be -1, so I'll assume it'll be +1 instead), does that mean my success rate... | 31,514 |
<p>Inspired by <a href="http://stats.stackexchange.com/questions/1194/practical-thoughts-on-explanatory-vs-predictive-modeling">this post</a> on the difference between explaining and predicting. I want to ask </p>
<ul>
<li>is mixed model <em>primarily</em> used to get better explanation (such as, but not limited to, g... | 73,900 |
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