Free reference · 596 entries
The words, before the course.
Short, plain definitions of the terms that turn up in statistics and data science — what they mean, and how they relate to each other. Nothing to sign in for.
75 of 596 entries under C
- Calibration SampleThe calibration sample is the subset of the data available to a data mining routine used as the training set.
- Categorical DataCategorical data are reflecting the classification of objects into different categories. For example, people who receive a mail order offer might be classified as “no response,” “purchase and pay,”…
- Categorical Data AnalysisCategorical data analysis is a branch of statistics dealing with categorical data. This sort of analysis is of great practical importance because a wide variety of data are of a categorical nature.
- Causal modelingCausal modeling is aimed at advancing reasonable hypotheses about underlying causal relationships between the dependent and independent variables.
- Census SurveyIn a census survey , all units from the population of interest are analyzed. A related concept is the sample survey, in which only a subset of the population is taken.
- Central Limit TheoremThe central limit theorem states that the sampling distribution of the mean approaches Normality as the sample size increases, regardless of the probability distribution of the population from which the…
- Central LocationCentral location is a synonym of central tendency.
- Central Tendency (Measures)Any measure of central tendency provides a typical value of a set of values . Normally, it is a value around which values are grouped.
- CentroidThe centroid of several continuous variables is the vector of means of those variables. The concept of centroid plays the same role, for example, in multiple analysis of variance (MANOVA) as the mean plays…
- CHAIDCHAID stands for Chi-squared Automatic Interaction Detector. It is a method for building classification trees and regression trees from a learning sample comprising already-classified objects.
- Chebyshev’s TheoremFor any positive constant ’k’, the probability that a random variable will take on a value within k standard deviations of the mean is at least 1 – 1/k2.
- Chernoff FacesChernoff faces are a category of icon plots. Each unit is represented as a schematic face.
- Chi-Square DistributionThe square of a random variable having standard normal distribution is distributed as chi-square with 1 degree of freedom.
- Chi-Square StatisticThe chi-square statistic (or -statistic) measures agreement between the observed and hypothetical frequencies.
- Chi-Square TestChi-square test (or -test) is a statistical test for testing the null hypothesis that the distribution of a discrete random variable coincides with a given distribution.
- Circular Icon PlotsCircular icon plots are a category of icon plots. Each variable is represented by a ray or direction; all rays start in the center.
- Classification and Regression Trees (CART)Classification and regression trees (CART) are a set of techniques for classification and prediction.
- Classification TreesClassification trees are one of the CART techniques. The main distinction from regression trees (another CART technique) is that the dependent variable is categorical.
- Cluster AnalysisIn multivariate analysis, cluster analysis refers to methods used to divide up objects into similar groups, or, more precisely, groups whose members are all close to one another on various dimensions being…
- Clustered SamplingClustered sampling is a sampling technique based on dividing the whole population into groups (“clusters”), then using random sampling to select elements from the groups.
- Cochran-Mantel-Haenszel (CMH) testThe Cochran-Mantel-Haenszel (CMH) test compares two groups on a binary response, adjusting for control variables.
- Cochran’s Q StatisticCochran’s Q statistic is computed from replicated measurements data with binary responses.
- Coefficient of DeterminationSST r2 = SSR , where SSR is the sum of squares due to regression, SST is the total sum of squares.
- Coefficient of variationThe coefficient of variation is the standard deviation of a data set, divided by the mean of the same data set.
- Cohen’s KappaCohen’s kappa is a measure of agreement for Categorical data. It is a special case of the Kappa statistic corresponding to the case of only 2 raters.
- Cohort dataCohort data records multiple observations over time for a set of individuals or units tied together by some event (say, born in the same year).
- Cohort studyA cohort study is a longitudinal study that identifies a group of subjects sharing some attributes (a “cohort”) then takes measurements on the subjects at various points in time and records data for the group.
- CointegrationCointegration is a statistical tool for describing the co-movement of data measured over time.
- Collaborative filteringCollaborative filtering algorithms are used to predict whether a given individual might like, or purchase, an item.
- CollinearityIn regression analysis, collinearity of two variables means that strong correlation exists between them, making it difficult or impossible to estimate their individual regression coefficients reliably.
- Column icon plotsSee sequential icon plots.
- Comparison-wise Type I ErrorIn multiple comparison procedures, the comparison-wise type I error is the probability that, even if the samples come from the same population, you will wrongly conclude that they differ.
- Complete Block DesignIn complete block design, every treatment is allocated to every block. In other words, every combination of treatments and conditions (blocks) is tested.
- Complete Linkage ClusteringThe complete linkage clustering (or the farthest neighbor method) is a method of calculating distance between clusters in hierarchical cluster analysis.
- Complete StatisticA sufficient statistic T is called a complete statistic if no function of it has zero expected value for all distributions concerned unless this function itself is zero for all possible distributions…
- Composite HypothesisA statistical hypothesis which does not completely specify the distribution of a random variable is referred to as a composite hypothesis.
- Concurrent ValidityThe concurrent validity of survey instruments, like the tests used in psychometrics, is a measure of agreement between the results obtained by the given survey instrument and the results obtained for the…
- Conditional ProbabilityWhen probabilities are quoted without specification of the sample space, it could result in ambiguity when the sample space is not self-evident.
- Confidence IntervalA confidence interval is an interval that brackets a sample estimate that quantifies uncertainty around this estimate.
- Consistent EstimatorAn estimator is a measure or metric intended to be calculated from a sample drawn from a larger population.
- Construct ValidityIn psychometrics, the construct validity of a survey instrument or psychometric test measures how well the instrument performs in practice from the standpoint of the specialists who use it.
- Content ValidityThe content validity of survey instruments, like psychological tests, is assessed by overview of the items by trained individuals and/or by the individuals from the target population.
- Contingency TableA contingency table is a tabular representation of categorical data. A contingency table usually shows frequencies for particular combinations of values of two discrete random variables X and Y.
- Contingency Tables AnalysisContingency tables analysis is a central branch of categorical data analysis, and is focused on the analysis of data represented as contingency tables.
- Continuous DistributionA continuous distribution describes probabilistic properties of a random variable which takes on a continuous (not countable) set of values – a continuous random variable.
- Continuous Random VariableA continuous random variable is any random variable which takes on values on a continuous scale.
- Continuous Sample SpaceIf a sample space contains an infinite number of sample points constituting a continuum, then such a sample space is said to be a continuous sample space.
- Continuous vs. Discrete DistributionsA discrete distribution is one in which the data can only take on certain values, for example integers.
- Control ChartsControl charts are used to track regular measurements of an ongoing process, and to signal when such a process had reached the point of going “out of control” (i.e.
- Convergent ValidityIn psychometrics, the convergent validity of a survey instrument or psychometric test indicates the degree of agreement between measurements of the same trait obtained by different approaches supposed to…
- Convolution of Distribution FunctionsIf F1(·) and F1(·) are distribution functions, then the function F(·) F(x) = ó õ F1(x–y) dF2(y) is called the convolution of distribution functions F1 and F2.
- Convolution of Distribution Functions (Graphical)If F1(·) and F1(·) are distribution functions, then the function F(·) is called the convolution of distribution functions F1 and F2.
- Correlation CoefficientThe correlation coefficient indicates the degree of linear relationship between two variables.
- Correlation MatrixA Correlation matrix describes correlation among M variables. It is a square symmetrical MxM matrix with the (ij)th element equal to the correlation coefficient r_ij between the (i)th and the (j)th variable.
- Correlation StatisticThe correlation statistic is one of the statistics used in the generalized Cochran-Mantel-Haenszel tests.
- Correspondence analysisCorrespondence analysis (CA) is an approach to representing categorical data in an Euclidean space, suitable for visual analysis.
- Correspondence PlotA correspondence plot represents the results of correspondence analysis (CA). For each category (possible value of a variable), its scores derived by CA for the first two dimensions are depicted as a point…
- Countable Sample SpaceIf a sample space contains finite or countably infinite number of sample points then such a sample space is referred to as a countable sample space.
- CovarianceThe covariance between two random variables X and Y is the expected value of the product of the variables’ deviations from their means.
- CovariateIn design of experiments, a covariate is an independent variable not manipulated by the experimenter but still affecting the response.
- Cover timeCover time is the expected number of steps in a random walk required to visit all the vertices of a connected graph (a graph in which there is always a path, consisting of one or more edges, between any two…
- Cox-RegressionSee Proportional hazard model
- Cramer – Rao InequalityEvery unbiased estimator has a variance greater than or equal to a lower bound called the Cramer – Rao lower bound.
- Criterion ValidityThe criterion validity of survey instruments, like the tests used in psychometrics, is a measure of agreement between the results obtained by the given survey instrument and more “objective” results for the…
- Critical RegionSee Acceptance region
- Cross sectional studyCross sectional studies are those that record data from a sample of subjects at a given point in time.
- Cross-sectional AnalysisCross-sectional analysis is concerned with statistical inference from cross-sectional data.
- Cross-sectional DataCross-sectional data refer to observations of many different individuals (subjects, objects) at a given time, each observation belonging to a different individual.
- Cross-tabulation TablesA cross-tabulation table represents the joint frequency distribution of two discrete variables.
- Cross-ValidationCross-validation is a general computer-intensive approach used in estimating the accuracy of statistical models.
- Crossover DesignIn randomized trials, a crossover design is one in which each subject receives each treatment, in succession.
- Cumulative Frequency DistributionA cumulative frequency distribution is a summary of a set of data showing the frequency (or number) of items less than or equal to the upper class limit of each class.
- Cumulative Relative Frequency DistributionA cumulative relative frequency distribution is a tabular summary of a set of data showing the relative frequency of items less than or equal to the upper class class limit of each class.
- Curb-stoningIn survey research, curb-stoning refers to the deliberate fabrication of survey interview data by the interviewer.
- Curse of DimensionalityThe curse of dimensionality is the affliction caused by adding variables to multivariate data models.
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