Statistics Definitions > Upper Tail and Lower Tail What is a “Tail”? The “tails” of a distribution are, just like the name suggests, the appendages on the side of a distribution. Although it can apply to a set of data,…

## Proportional Reduction in Error (PRE Test)

Statistics Definitions > What is the Proportional Reduction in Error (PRE Test)? The Proportional Reduction in Error (PRE Test) is a statistical criterion which quantifies the extent that knowledge about one variable can help us predict another variable. That is…

## Varimax Rotation: Definition

Statistics Definitions > Varimax rotation is an important second step in Factor Analysis and Principal Component Analysis. The initial factor analysis step has an infinite number of initial, or provisional, factors. Factor rotation, including Varimax rotation, transforms the initial factors…

## Regularized Regression

Regression Analysis > What is Regularized Regression? Regularized regression is a type of regression where the coefficient estimates are constrained to zero. The magnitude (size) of coefficients, as well as the magnitude of the error term, are penalized. Complex models…

## Linear Discriminant Analysis

Statistics Definitions > What is Linear Discriminant Analysis? In statistics, pattern recognition and machine learning, linear discriminant analysis (LDA), also called canonical Variate Analysis (CVA), is a way to study differences between objects. This sorting method uses a linear combination…

## Subgroup Analysis

Experimental Design > Subgroup analysis is research that focuses on one or more subgroups of the main data set. It attempts to find and illustrate patterns within and between subgroups. It is widely used in medical research; the price tag…

## Quintile: Definition, Examples in Economics, Health

Statistics Definitions > A quintile is a 1/5th (20 percent) portion of the whole. In statistics, it’s a population or sample divided into five equal groups, according to values of a particular variable. It can also be used to refer…

## Lurking Variable: Simple Definition, Examples

Types of Variables > What is a Lurking Variable? A lurking variable is a variable that is unknown and not controlled for; It has an important, significant effect on the variables of interest. They are extraneous variables, but may make…

## Agglomerative Clustering

Hierarchical Clustering > What is Agglomerative Clustering? Agglomerative clustering (also called (Hierarchical Agglomerative Clustering, or HAC)) is a “bottom up” type of hierarchical clustering. In agglomerative clustering, each data point is defined as a cluster. Pairs of clusters are merged…

## Intention to Treat

RCTs > Intention to treat (ITT) analysis is a method of statistical analysis often used in medical research. In ITT analysis, a study participant is analyzed as belonging to whatever treatment group he/she was randomized into, whether or not the…