question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I want to cluster <em>Facebook</em> user based on the number of mutual friends. If two users have more number of mutual friends then they are designated more closer to each other. I am thinking about using k-medoids clustering algorithm. In R I can use PAM for k-medoid clustering which needs data as a distance matr... | 74,408 |
<p>I need to do a weighted multiple linear regression. If I want to weigh certain observations differently, am I correct that I simply have to multiply the y(i) of that observation, and the corresponding row in X, with that weight?</p> | 74,409 |
<p>I have been running a linear regression where my dependent variable is a composite. By this I mean that it is built up of components that are added and multiplied together. Specifically, for the composite variable A:</p>
<pre><code>A = (B*C + D*E + F*G + H*I + J*K + L*M)*(1 - N)*(1 + O*P)
</code></pre>
<p>None of ... | 49,090 |
<p>I need some guidance on the appropriate level of pooling to use for difference of means tests on time series data. I am concerned about temporal and sacrificial pseudo-replication, which seem to be in tension on this application. This is in reference to a mensural study rather than a manipulative experiment.</p>
... | 37,281 |
<p>I am fitting a few time series using <code>fitdistr</code> in R. To see how different distributions fit the data, I compare the log likelihood from the <code>fitdistr</code> function. Also, I am fitting both the original data, and the standardized data (ie. (x-mean)/sd).</p>
<p>What I am confused about is that, the... | 5,353 |
<p>Let us take two formulations of the $\ell_{2}$ SVM optimization problem, one constrained: </p>
<p>$\min_{\alpha,b} ||w||_2^2 + C \sum_{i=1}^n {\xi_{i}^2}$ </p>
<p>s.t $ y_i(w^T x_i +b) \geq 1 - \xi_i$<br>
and $\xi_i \geq 0 \forall i$</p>
<p>and one unconstrained: </p>
<p>$\min_{\alpha,b} ||w||_2^2 + C \sum_{i=1... | 74,410 |
<p>(redirected here from mathoverflow.net)
Hello, </p>
<p>At work I was asked the probability of a user hitting an outage on the website. I have some following metrics. Total system downtime = 500,000 seconds a year. Total amount of seconds a year = 31,556,926 seconds. Thus, p of system down = 0.159 or 1.59%
We can al... | 74,411 |
<p>I need some help here.</p>
<p>I have some data in which every entry can take one or more levels of a categorical variable. for example, I have a category with 3 levels:</p>
<pre><code>entry category
1 A, B, C
2 B
3 C, A, B
</code></pre>
<p>How should I organized it into a file in order to easi... | 74,412 |
<p>I am trying to analyze a set of nonnegative continuous non-integer data (i.e. the data points are not counts) that are mostly between 0 and 3 whose distribution is highly right-skewed even after log transformation. I am thinking that one possibility may be hurdle model to model the zeros and positive data points sep... | 74,413 |
<p>I am working on a project which requires me to watch video of athletes and measure the straightness/smoothness/waviness, whatever term is acceptable, of their spine. Dividing the spine into segments may also be acceptable if it provides the best results.</p>
<p>Right now I can plot x and y points on still images. N... | 37,283 |
<p>I have a general question regarding a varying intercept / varying slope model in jags/stan:</p>
<p>I have data from a psychophysics experiment, with one covariate, one within-subjects factor and several subjects:</p>
<p>The response variable y is binary, and I want to model the probability of giving a response as ... | 74,414 |
<p>If polynomial regression models nonlinear relationships, how can it be considered a special case of multiple linear regression?</p>
<p>Wikipedia notes that "Although polynomial regression fits a nonlinear model to the data, as a statistical estimation problem it is linear, in the sense that the regression function ... | 74,415 |
<p>I have been studying Statistics recently, using a few introductory texts. </p>
<p>My issue is these texts only seem to provide analysis methods that are suitable to linear relationships: Pearson r correlation coefficients etc. Additionally all the Statistical methods presented seem to be based on the normal Gaussia... | 37,284 |
<p>Given $T=G+A$ where $A$ and $G$ are independent random variables, I'd like to estimate the distribution of $G$ given empirical (measured) distributions of $T$ and $A$. Of note: all three random variables are guaranteed to be bounded on $[0,\infty]$ (unlike the more studied case where $A$ would be a zero mean gaussia... | 74,416 |
<p>I have a sample $x=(4, 3, 1, 2, 2, 2, 2, 5, 7, 3, 1, 2, 3, 4, 3, 2, 3, 3, 3, 4)$ of size $n=20$. from a binomial distribution with 10 trials and probability of success $p$. I am asked to construct the asymptotic 95% confidence interval based on the likelihood. I think this should be the set
$$
C = \left\{ p \in (0,1... | 37,285 |
<p>I am trying to test whether there is a significant interaction between an ordinal (<code>A</code>) and categorical variable (<code>B</code>) in R using <code>glm</code>. When I create a model that only includes the interaction term <code>A:B</code>, the model runs fine and I get a reasonable estimate. When I run the... | 74,417 |
<p>Following are the results from Fisher-type unit-root test for RDI (dependent variable). <strong>How do you interpret it?</strong> </p>
<pre><code>Based on Phillips-Perron tests:
Ho: All panels contain unit roots Number of panels = 100
Ha: At least one panel is stationary Avg. number of pe... | 49,932 |
<p>Following the question <a href="http://stats.stackexchange.com/questions/24516/interaction-of-categorical-and-continuous-variable-using-glm-in-spss">here</a>, how to I refer to GLM in my project? </p>
<p>Just a recap:</p>
<p>GLM is a general model that includes a number of regression techniques. I have used it to ... | 74,418 |
<p>I'm fitting a multiple linear regression model between 4 categorical variables (with 4 levels each) and a numerical output. My dataset has 43 observations.</p>
<p>R gives me the following $p$-values from the $t$-test for every slope coefficient: $.15, .67, .27, .02$. Thus, the coefficient for the 4th predictor is s... | 49,368 |
<p>I'm working with a dataset consisting of degradation rates for proteins in an organism, a total of approx 3750 rates in total. Obtaining these rates is difficult, so the majority of rates are reported with only n=1, however a small subset have been reported with n=2, so the sample standard deviation for each protein... | 74,419 |
<p>Normally when I do factor analysis, I have a whole bunch of variables that need to be reduced. But here I only have two binary variables (yes/no) that I need to reduce into one interval factor. Is Principle Components / Factor Analysis appropriate for this? When I do it, my extraction communalities are really high. ... | 49,110 |
<p>A set is said to be fully-symmetric if for every x in it, negating one of its components results in y such that y is in the set as well.</p>
<p>A set is said to be semi-symmetric if for every x in it, negating all of its components (at once) results in y such that y is in the set as well.</p>
<p>Now examine the op... | 49,111 |
<p>Suppose I have <em>repeated</em> time observations for 800 meter sprint for a group of athletes over the course of a season. <strong>I would like to test the hypothesis that all the times are drawn from the same unspecified distribution (i.e., that the distributions of each athlete's finishing times are all the same... | 74,420 |
<p><img src="http://i.stack.imgur.com/1vzQ1.jpg" alt="Table"></p>
<p>I am trying to come up with a method for deciding the winner from among eight student groups competing for a prize.</p>
<p>The raw data and corresponding percentages measure participation per group in a campus program. </p>
<p>The current rules say... | 74,421 |
<p>Is there a way of investigating publications bias in a meta-analysis of single case studies? Usually one can assess publication bias using funnel plots or Egger's test to assess funnel plot asymmetry. However those methods require some estimate of the individual studies' variance. In case of single case studies such... | 74,422 |
<p>I have started with a time series of 5000 random numbers drawn from uniform distribution with mean 0 and variance of 1.</p>
<p>I then construct a Variance-Covariance matrix and use this to induce correlation into the random series.</p>
<p>I want the correlated series to have an acf of the form exp(-mk), where m is... | 74,423 |
<p>Assume we have two variables A and B, and we are trying to find the Mutual Information between them. Can the mutual information enable us to find if there exists a positive or negative relationship between two variables?</p> | 74,424 |
<p><strong>Background:</strong> I asked hundreds of participants in my survey how much they are interested in selected areas (by five point Likert scales with 1 indicating "not interested" and 5 indicating "interested").</p>
<p>Then I tried PCA. The picture below is a projection into first two principal components. Co... | 74,425 |
<p>I am trying to perform a multiple regression in <code>R</code>. However, my dependent variable has the following plot:</p>
<p><img src="http://i.stack.imgur.com/AMXDm.jpg" alt="DV"></p>
<p>Here is a scatterplot matrix with all my variables (<code>WAR</code> is the dependent variable):</p>
<p><img src="http://i.st... | 74,426 |
<p>I recently did some experimenting comparing some common method of internal validation. In my field, the use of a single 1:1 holdout validation is extremely common, even with very small datasets, and I wanted to show my colleagues that there might sometimes be alternatives.</p>
<p>I had a large dataset of approx 30,... | 74,427 |
<p>I have a correlated multivariate Bernoulli random variable $\textbf{X} = (X_1, ..., X_N)$, where the $X_i$ are Bernoulli random variables with parameters $p_i$ and $N \times N$ covariance matrix $\textbf{C}$.</p>
<p>How do choices of $p_i$ constrain choices of $C$ and vice-versa?</p>
<p>In one extreme case, where ... | 74,428 |
<p>I have a longitudinal data set of individuals and some of them were subject to a treatment and others were not. All individuals are in the sample from birth until age 18 and the treatment happens at some age in between that range. The age of the treatment may differ across cases. Using propensity score matching I wo... | 74,429 |
<p>I have the following histogram of count data. And I would like to fit a discrete distribution to it. I am not sure how I should go about this. <img src="http://i.stack.imgur.com/C3up0.png" alt="enter image description here"></p>
<p>Should I first superimpose a discrete distribution, say Negative Binomial distributi... | 74,430 |
<p>Suppose I have a data set, and have trained up a regression model (happens to be a bayesian linear model, I'm just using the R package). The model outputs a wide range of values, greater than 0 and less than 0, although the actual output can only be greater than 0.</p>
<p>Is there an accepted away to apply bounds t... | 37,295 |
<p><strong>I have logs from an autocomplete form, which I would like to leverage to increase the intelligence of the results it returns.</strong></p>
<p>I have a project that revolves around users selecting opera characters from a database of ~15,000 unique characters. My difficulty is that each character appears in t... | 37,298 |
<p>I am looking for a simple code example of how to run a Particle Filter in R. The pomp package appears to support the state space math bit, but the examples are a little tricky to follow programmatically for a simple OO developer such as myself, particularly how to load the observed data into a pomp object.</p>
<ul>... | 49,125 |
<p>I would like to find a <em>hierarchical-clustering</em> method useful to assign a group membership into <em>k</em> groups for all individuals in my dataset. I have considered several classic ordination methods, PCA, NMDS, "mclust", etc., but three of my variables are categorical (<em>see data description below</em>)... | 49,126 |
<p>Suppose I care about mispredicting one class much more than another.
Is there a way I can communicate this information to the standard classification techniques?</p>
<p>The only way I can think of is adjusting the threshold, but I wonder if there is a better way.</p> | 74,431 |
<p>I'm a newbie so I have only basic statistical skills.</p>
<p>I'm wondering if it is possible to use any stat test to analyze the previous matches between 2 tennis players to build a solid betting tip that proves to be profitable in the long run.</p>
<p>I don't expect an answer that makes me billionair (lol, 4 sure... | 37,299 |
<p>Does anyone know of recommendations/references for plotting <em>binary</em> time series data? Or categorical time series data? I'm looking at win/loss records, and it seems like there should be plots that exploit the binary nature beyond just a simple line plot.</p>
<p>Late edit: I'm familiar with Tufte's suggestio... | 74,432 |
<p>I have a function of a dozen discrete variables, $$y = f(x_1, ..., x_n)$$ and $k$ samples of $y$ (a lot), $y$ being continuous.</p>
<p>I can use Matlab to analyse the data, with the statistics toolbox. The goal is to analyse the relationship between $y$ and my variables. For example, which variables $x_m$ explain b... | 37,301 |
<p>Is the validity coefficient the same thing as $\rho$, where $\rho = \frac{COV_{XY}}{SD_X SD_Y}$?</p> | 37,303 |
<p>Let $X$ and $Y$ be two i.i.d.
chi-square distributed random variables with four degrees of freedom.
How can we get the joint probability distribution function of the random variables $U=(X-Y)/(X+Y)$, $V=X+Y$?</p> | 74,433 |
<p>If machine is viewed as function approximation, what class of functions are modeled by a neural network?</p> | 74,434 |
<p>I have data on about 20000 consumers who were exposed to some form of advertising. The data is in the following form.</p>
<pre><code>Cookie_Id Observation_Number Ad_Id Ad_Id_Lookup Placement_Id Placement_Category Placement_Cpi Cookie_Lookup
2 1 325 Standard 3722 News 20 0
3 1 325 Sta... | 74,435 |
<p>I have three ARMA(p,q) models for the variable X and using each model I produce forecasts for 12 months ahead. Note that in all three models the residual is normally distributed.</p>
<p>Now if I want to produce an <strong><em>average forecast</em></strong> and a <strong><em>standard deviation</em></strong> for the ... | 18,700 |
<p>I'm learning clustering analysis and one book I read says the clustering model should be applied to a disjoint data set to examine the consistency of the model. </p>
<p>I think in clustering analysis we don't need to split the data into train and test sets like in supervised learning since without labels there is n... | 166 |
<p>I believe one major advantage of Bayesian inference is the intuitiveness of interpretation. This is my primary interest. However, it's not completely clear to me when it's OK to make such an interpretation.</p>
<p>I make the potentially false assumption that fitting a probability model in the frequentist way is vir... | 74,436 |
<p>I am doing a research on two groups, one experimental and one control, which are not randomly selected. In fact the two groups are <em>intact groups</em>. The purpose is to find the effect of the number of languages that the learners know on their academic achievement. The selected design is <a href="http://www.soci... | 74,437 |
<p>I have been working with fuzzy logic (FL) for years and I know there are differences between FL and probability specially concerning the way FL deals with uncertainty. However, I would like to ask what more differences exist between FL and probability?</p>
<p>In other words, if I deal with probabilities (fusing inf... | 74,438 |
<p>I was thinking this may be similar to a Mark and recapture problem where there is a known upper bound, hence the title.</p>
<p>I am doing a proportion but sometimes the estimate is larger than the known upper bound. Is there a way to restrict the possible answers to be between the two bounds?</p>
<p>Example: Assum... | 74,439 |
<p>I've been analysing some data using linear mixed effect modelling in R. I'm planning to make a poster with the results and I was just wondering if anyone experienced with mixed effect models could suggest which plots to use in illustrating the results of the model.
I was thinking about residual plots, plot of fitted... | 74,440 |
<p>I have 50 measurements of 10 descriptors and 1 binary output variable.</p>
<p>I want to use a classification procedure to be able to predict the output, so I split the data into a training and a test set and I can then generate my classifier (I am using a decision tree) and test it on the test set.</p>
<p>Now, obv... | 37,315 |
<p>In King and Zheng's paper:
<a href="http://gking.harvard.edu/files/gking/files/0s.pdf" rel="nofollow">http://gking.harvard.edu/files/gking/files/0s.pdf</a></p>
<p>They mention about $\tau$ and $\bar{y}$. I already have data with 90000 0's and 450 1's. I have already fitted a logistic regression with the whole data... | 37,316 |
<p>I have two categorical variables and was looking into doing a chi-square test. I then noticed I had some low frequencies in my contingency table and thought Fisher's Exact Test may be useful. I've now come full circle after doing some reading and want to use Pearson's Chi Squared with n-1 correction. Is there a way ... | 74,441 |
<p>Let suppose we are given two vectors <strong>u</strong>, <strong>v</strong> $\in \mathbb{R}^n$ and we want a function that returns $0$ if the ordering of the elements of both vectors are the same or a positive number otherwise, where the larger the number of mismatches the larger the positive value. We want to ensur... | 74,442 |
<p>I am evaluating the accuracy of GPS watches, taking many readings over a known distance. I've been calculating standard deviation using the mean reading, but because I know what the reading should be, I could use that instead of the mean.
Would this be a reasonable thing to do?</p> | 74,443 |
<p>Usually all the tests we are using have increasing power as the sample size increases. But what if a test is not consistent?
Is it not worthy to develop such a test? Or can it be justified to use an inconsistent test under some circumstances? In particular, as inconsistency is often due to the distributional model? ... | 74,444 |
<p>I'm building a logit model using R and I'm getting a result of 88.9% of accuracy (verified using the ROC [in rattle, evaluation tab] using 30% of my 34k dataset).</p>
<p>What kind of tests would be interesting to do to certify myself that it's a good model?</p> | 74,445 |
<p>If the outcome of a market could be expressed as a probability it might be: </p>
<p>Outcome - Description - Probability as a %</p>
<ol>
<li>Up a lot 20% (a move of say more than 10%) </li>
<li>Down a lot 20% </li>
<li>Up a bit 20% (a move of between 0 and 10%) </li>
<li>Down a bit 20% </li>
<li>Sideways 20% </li>
... | 37,319 |
<p>I am familiar with meta analysis and meta regression techniques (using the R package <code>metafor</code> from Viechtbauer), but I recently stumbled on a problem I can't easily solve. Say we have a disease that can go from mother to the unborn child, and it has been studied already a number of times. Mother and chil... | 74,446 |
<p>I originally asked this on a machine learning site, but one of the responses made me think that maybe this site is more suitable.</p>
<p>Suppose you have two weighted coins, and every day you flip each one a number of times and record the total number of heads. So on the tenth day you might have flipped coin A 106 ... | 37,440 |
<p>In R, the <code>step</code> command is supposedly intended to help you select the input variables to your model, right? </p>
<p>The following comes from
<code>example(step)#-> swiss</code> &
<code>step(lm1)</code></p>
<pre><code>> step(lm1)
Start: AIC=190.69
Fertility ~ Agriculture + Examination + Ed... | 37,706 |
<p>I don't have much experience with panel data so I apologize in advance if this sounds ridiculous.</p>
<p>Let's say that I am trying to control for individual and temporal fixed effects when running a panel data regression and I have 998 individuals and 29 years of data. In Stata the way to deal with multi-variate f... | 74,447 |
<p>I start with a vector of random numbers sampled from a normal distribution:</p>
<pre><code>R<-rnorm(100, mean=0, sd=30)
</code></pre>
<p>I would now like to create 3 variables that are correlated with each other with a pre-specified correlation. In addition I would like to have these three variables correlated ... | 49,933 |
<p>Suppose you have a set of numbers $\{1,2,...,m\}$ where $m \ge 5$ . Now you randomly choose five of those elements with replacement, $\text{a}_1$ ... $\text{a}_5$.</p>
<p>What is the distribution of max($\text{a}_1$,$\text{a}_2$,$\text{a}_3$,$\text{a}_4$,$\text{a}_5$)?</p> | 37,325 |
<p>I have an independent sequence of random variables such that P($X_n = \pm1) = \frac{1-2^{-n}} {2} $<br>
and P($X_n = 2^ k)=2^{-k}$ for k = n+1,n+2,...
Define a new sequence of random variables by $Y_n = X_n$ if $X_n = \pm1$<br>
$Y_n = 0$ otherwise.
Find P($Y_n = y)$</p>
<p>How to do this?
I have so far proven $X_... | 74,448 |
<p>I am doing a project on low birth weight cohort and normal birth weight tested at 3 different age groups on one cognitive test. Is this considered a 2x3 ANOVA if I want to know birth group differences? Do I need to do t-tests or one-way anova first to test if there is an actual birth group different with age collap... | 74,449 |
<p>I understand that it's instead correct to cross-validate using new data. Why is it
so? It is just that a model will tend to fit the data set that was used to created it better than another randomly sampled set of data?</p>
<p>Could it ever be justified to use the same data for EFA and CFA?</p> | 74,450 |
<p>I am an actuary working on a Bayesian loss reserve model using incremental average severity data. Exploratory analysis of the response seems to suggest a skew normal distribution of some sort would be appropriate, as there are some negative values in the left tail, and the log transformed positive values fit a norma... | 74,451 |
<p>My question is: is it possible to pool observations when it is the same countries that are observed through the years.
I have observations on 37 countries in 2010, 47 countries in 2011 and 60 countries in 2012. However, it is the same countries that have been observed (more countries are though added). </p>
<p>Whi... | 74,452 |
<p>I have a data set of around 5000 features. For that data I first used Chi Square test for feature selection; after that, I got around 1500 variables which showed significance relationship with the response variable. </p>
<p>Now I need to fit logistic regression on that. I am using glmulti package for R (glmulti pac... | 74,453 |
<p>The height for 1000 students is approximately normal with a mean 174.5cm and a standard deviation of 6.9cm. If 200 random samples of size 25 are chosen from this population and the values of the mean are recorded to the nearest integer, determine the probability that the mean height for the students is more than 176... | 74,454 |
<p>I understand that when sampling from a finite population and our sample size is more than 5% of the population, we need to a correction on the sample's mean and standard error using this formula:</p>
<p>$\hspace{10mm} FPC=\sqrt{\frac{N-n}{N-1}}$
</p>
<p>Where N is the population size and n is the sample size.</p>
... | 37,333 |
<p>I've called my question "clustering" but I am not sure if that's the right term. Imagine my matrix looks like this:</p>
<pre><code>[ 0. , 0.92, 0. , 0.85, 0. ]
[ 0.92, 0. , 0. , 0.89, 0. ]
[ 0.85, 0. , 0. , 0.89, 0. ]
[ 0. , 0. , 0. , 0. , 0. ]
[ 0. , 0.89, 0. , 0.89, 0. ]
</cod... | 23,909 |
<p>I have a biometric authentication system that is using a person's gait to authenticate them. I extract features from gait, run it through a comparison versus a template and produce a similarity score (where if this similarity score is below a certain threshold, then the user is authenticated). So, I have 72 trials t... | 51 |
<p>I am conducting a study on a cohort of people with a follow-up period of 7 years. I wish to use Cox Proportional Hazard model to estimate HR between an exposure and the length of time of an event. One missing information is the date of birth for the all subjects, but month and year are available.This prevents the ca... | 49,162 |
<p>What statistical research blogs would you recommend, and why?</p> | 74,455 |
<p>I have been looking into theoretical frameworks for method selection (note: not model selection) and have found very little systematic, mathematically-motivated work. By 'method selection', I mean a framework for distinguishing the appropriate (or better, optimal) method with respect to a problem, or problem type.</... | 49,167 |
<p>We want to compare two distributions of ages (birth years) of individuals. Given a set of individuals (<em>all</em>) and a subset of that set (<em>subset</em>), we want to find out:</p>
<ol>
<li>Is it valid to compare the age distribution of <em>all</em> with that of <em>subset</em> (when |<em>subset</em>| is much ... | 74,456 |
<p>In the definition of standard deviation, why do we have to <strong>square</strong> the difference from the mean to get the mean (E) and take the <strong>square root back</strong> at the end? Can't we just simply take <strong>the absolute value</strong> of the difference instead and get the expected value (mean) of t... | 49,295 |
<p>In logistic regression, if we considered residuals, could they only take on the values $0$ or $1$? The data points themselves take on only $1$ or $0$. The logistic curve can take on any value between $0$ and $1$. What would the distribution of the residuals look like?</p> | 74,457 |
<p>I hope that this is a right place and way to ask this question. I am trying to understand how to derive the probability density function of x(t) in an AR model of order K given (t-k) past observations.<br>
I am primarily referring to this <a href="http://reference.kfupm.edu.sa/content/u/n/a_unifying_framework_for_d... | 74,458 |
<p>I have a data set with 24 predictor variables, all continuous, but with different scales and potential collinearity. I’m trying to decide whether to use <code>randomForest</code> or <code>cforest</code> in <a href="http://cran.r-project.org/web/packages/party/index.html" rel="nofollow">party</a> with conditional imp... | 74,459 |
<p>I did multinomial logistic regression using SPSS chi-square is .000 , df is 0 and significance =. </p>
<p>So what does it mean significance = .? </p> | 37,344 |
<p>My book outlines a procedure but a preliminary part of it is unclear to me. </p>
<p>Let X be the number of occurences of an event over a unit of time and assume that it has a Poisson distribution with mean $m=\lambda $. Let $T_1, T_2 , T_3, \ldots $ be the interarrival times of the occurences and they are iid with ... | 74,460 |
<p>I have obtained optimally scaled variables from a highly mixed nature of data containing binary, nominal, ordinal and scale type variables. The optimal scaling was obtained in SPSS through a CATPCA procedure. Now I want to use these variables in a Factor Analysis and want to use a rotation to obtain meaningful loads... | 37,345 |
<p>I have a data set containing a daily sensor data measurements recorded from 20 participants for 60 days (baseline data).</p>
<p>I am trying to develop methods for predicting/estimating decline in
long-term monitoring studies, i.e. can measurement of a parameter on a daily basis be used to detect/predict decline (i... | 74,461 |
<p>I am working on a problem where we are interested in finding the MLE for a function of two parameters.</p>
<p>I am having problems with going about finding this. Intuitively, the idea makes sense. I am just wondering about the definition of the MLE of a function of two parameters (Google isn't turning up much). The... | 27,621 |
<p>I am currently trying to better understand probabilistic skill ranking systems for games, but I find that I have trouble properly understanding the basic concept of how skill as a pairwise comparison can be generalized.</p>
<p>For instance, if all you know is that player C wins player B 80% of the time, while that ... | 74,462 |
<p>I have a question regarding how to evaluate agreement between an individual's rating, and that of a group of people (of which the individual was a part). The group score was achieved through consensus (i.e. they agreed on one score as a group). I was originally planning to use kappa to look at agreement between the ... | 74,463 |
<p>I'm looking at the concentration of an event occurrences in a given interval of time. For example, we suppose that an event occurred 4 times in an interval of length 10. I can represent this as a string where <code>X</code> means <em>the event occurred</em> whereas <code>o</code> means <em>the event didn't occur</em... | 74,464 |
<p>I would be very grateful for some advice on how to model mixture distributions with R.</p>
<p>Given a problem to create a ranking of graduate students by their yearly income after completing their education, what are some suited models for this task?</p>
<p>Specifically, my data has a distribution with a point mas... | 74,465 |
<p>Based on estimated classification accuracy, I want to test whether one classifier is statistically better on a base set than another classifier . For each classifier, I select a training and testing sample randomly from the base set, train the model, and test the model. I do this ten times for each classifier. I th... | 37,346 |
<p>A random sample of <strong>388</strong> married couples found that <strong>292</strong> had two or more personality preferences in common. In another random sample of <strong>552</strong> married couples, it was found that only <strong>24</strong> had no preferences in common. Let p1 be the population proportion of ... | 74,466 |
<p>I am fairly new to data analysis and visualization, and I'm trying to figure out the best model to show some data regarding page load time (in seconds).</p>
<p>The current view is a line graph where the x-axis is the page, and the y-axis is the load time. This graph is visually misleading though, because in my mind... | 37,349 |
<p>what is the pdf of the product of two independent random variables X and Y, if X and Y are independent?
X is normal distributed and Y is chi-square distributed.</p>
<p>Z = XY</p>
<p>if $X$ has normal distribution $$X\sim N(\mu_x,\sigma_x^2)$$
$$f_X(x)={1\over\sigma_x\sqrt{2\pi}}e^{-{1\over2}({x-\mu_x\over\sigma_x}... | 47,393 |
<p>A probability distribution is a member of the two-parameter exponential family if the distribution can be expresses in the following form:</p>
<p>$$ h(\theta, \phi) \text{exp}\left[\sum t(x_{i})\psi(\theta, \phi) + \sum u(x_{i})\chi(\theta, \phi)\right] $$ </p>
<p>for parameters: $\theta$ and $\phi$, data: $x_{1},... | 37,351 |
<p>I’m using Stata 12.0, and I’ve downloaded the <code>polychoricpca</code> command written by Stas Kolenikov, which I wanted to use with data that includes a mix of categorical and continuous variables. Given the number of variables (around 25), my hunch is that I will need to generate more than 3 components. Ultimate... | 37,352 |
<p>I am building a cox survival analysis model with a retailer's transaction data. Almost all the variables have failed the proportionality test. Can I continue with the Cox model? Should I build a LIFEREG model instead of the Cox model?</p> | 74,467 |
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