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A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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 missing-data× 345 When the data present lack of information (gaps), i.e., are not complete. Hence, it is important to consider this feature when performing a analysis or test. simulation× 334 A vast area which includes generating results from computer models. panel-data× 332 Panel data refers to multi-dimensional data frequently involving measurements over time in econometrics. It is also called longitudinal data in biostatistics. covariance× 332 a quantity used to measure the strength and direction of the linear relationship between two variables. The covariance is unscaled, & thus often difficult to interpret; when scaled by th… sas× 331 a proprietary cross-platform general-purpose statistical software package. [Official Website](http://www.sas.com/index.html) autocorrelation× 321 the correlation of a series of data with itself at some lag. This is an important topic particularly in the analysis of time-series data. mcmc× 321 Markov Chain Monte Carlo refers to a class of methods for generating samples from a target distribution by generating random numbers from a Markov Chain whose stationary distribution is the target dis… random-variable× 320 a value that is subject to chance variation (i.e., randomness in a mathematical sense). multilevel-analysis× 319 Statistical methods appropriate for the analysis of data sets comprising several levels of hierarchy of units of analysis (e.g., students nested in classes nested in schools; observations nested in pa… outliers× 310 an observation that appears to be unusual or not well described relative to a simple characterization of a dataset. pdf× 310 PDF stands for Probability Density Function. The PDF of a variable gives the relative probability for each value of a continuous variable. Use this tag when asking about probability functions in gener… ordinal× 308 ordinal refers to data that have an order but not necessarily equal spacing between levels. It can also refer to ordinal logistic regression. inference× 302 Inference, in a statistical context, refers to drawing conclusions from data containing an element of randomness introduced by e.g. measurement error, sampling variation, or assignment of experimental… algorithms× 294 a a set of one or more computations that will produce a calculated result. All statistics methods are algorithms. Algorithms can be simple, such as calculating a percentage, or can be … goodness-of-fit× 291 Goodness of fit tests indicate whether or not it is reasonable to assume that a random sample comes from a specific distribution. residuals× 285 the actual values minus the predicted values. Many statistical models make assumptions about the error, which is estimated by the residuals. random-effects-model× 280 Parameters associated with the particular levels of a covariate are sometimes called the “effects” of the levels. If the levels that are observed represent a random sample from the set of all possible… lmer× 270 functions in the R package lme4 that fit mixed effects models (ie, models that include fixed & random effects). These models can be non-linear in the sense that the… expected-value× 269 a weighted average of all possible values a random variable can take on, with the weights equal to the probability of taking on that value. regression-coefficients× 269 The parameters of a regression model. nonlinear-regression× 261 only for regression models (q.v.) in which the response is a nonlinear functions of the *parameters* (not because it's a nonlinear function of the *predictors*). cart× 259 Stands for 'Classification And Regression Trees'. CART is a technique for developing a tree model (T) to predict categories (C) and/or continuous values (R) by recursive partitioning. It does not make… text-mining× 252 Refers to a subset of data mining concerned with extracting information from data in the form of text by recognizing patterns. The goal of text mining is often to classify a given document into one of… multinomial× 251 A multivariate, discrete probability distribution used to describe the results of a random experiment where each of $n$ outcomes are placed into one of $k$ nominal categories. heteroscedasticity× 250 a random process that has non-constant variance along some continuum. monte-carlo× 247 Using (pseudo-)random numbers to simulate the random behavior of a real system. normalization× 247 A way of re-expressing data to make their values lie between 0 and 1 (or 0% and 100%). proportion× 246 the fraction of some total that is of a particular kind, either (i) as a count of one type of thing out of a total count, or (ii) as a component of a continuous variable. stochastic-processes× 246 A stochastic process describes evolution of random variables/systems over time and/or space and/or any other index set. It has applications in areas such as econometrics, weather, signal processing, e… error× 235 the deviation of the observed value from the (unobservable) true function value. Do NOT use this tag for SOFTWARE ERROR messages. spatial× 233 The field of study concerning statistical methods that use space and spatial relationships (such as distance, area, volume, length, height, orientation, centrality and/or other spatial characteristics… model× 231 a formalization of relationships between variables in the form of mathematical equations. The model is statistical as the variables are not deterministically but stochastically … likert× 227 Classically, a Likert scale was composed of the sum of many Likert items (ordinal ratings of the amount of agreement with a statement), where all the items were equally valid. Today the term sometimes… lasso× 226 A form of regularization used in the estimation of regression coefficients that shrinks coefficient estimates by penalizing their absolute value (i.e. the $L_1$ norm of the estimates). Some coefficien… terminology× 223 Indicates questions asking about the use and meaning of specific technical words/concepts in statistics. sample× 218 a subset of a population. Statistics, in general, is concerned with using samples to make inference about the parameters governing a larger (possibly infinite) population.