Statistics How To

Descriptive Statistics > Interquartile Mean You may want to read this article first: What is the trimmed mean? What is the Interquartile Mean? The interquartile mean (IQM) is the mean of the middle 50 percent of data in a data set. Unlike the “regular” arithmetic mean, it is resistant to outliers. How to Find the … Read more

Descriptive Statistics > Upper Hinge and Lower Hinge What are the Upper Hinge and Lower Hinge? Tukey’s upper hinge and lower hinge are measures of position. The hinges are created when you split a data set into four pieces (with three hinges). As the median is included in this “splitting,” Tukey’s hinges are sometimes called … Read more

Post Hoc Tests What is Dunn’s Test? Once your initial ANOVA has found a significant difference in three or more means, Dunn’s Test can be used to pinpoint which specific means are significant from the others. Dunn’s Multiple Comparison Test is a post hoc (i.e. it’s run after an ANOVA) non parametric test (a “distribution … Read more

Post Hoc > What is Dunnett’s Test? Dunnett’s Test (also called Dunnett’s Method or Dunnett’s Multiple Comparison) compares means from several experimental groups against a control group mean to see is there is a difference. When an ANOVA test has significant findings, it doesn’t report which pairs of means are different. Dunnett’s can be used … Read more

Correlation Coefficients > This article is about Lin’s concordance correlation coefficient, which measures bivariate pairs of observations relative to a “gold standard” test or measurement. A similarly named statistic is the coefficient of concordance (often called the “W statistic“), which is used to assess agreement between different raters. What is the Concordance Correlation Coefficient? Lin’s … Read more

Introduction to Probability > Probability Space What is a Probability Space? In order to comprehend a statement like “the probability of rolling a die twice and getting two sixes is about 3%”, you need to specify a probability space. A probability space models random events and is made up of three parts: Sample space: the … Read more

Hierarchical Cluster Analysis > Complete linkage clustering Complete linkage clustering (farthest neighbor ) is one way to calculate distance between clusters in hierarchical clustering. The method is based on maximum distance; the similarity of any two clusters is the similarity of their most dissimilar pair. Complete Linkage Clustering vs. Single Linkage Complete linkage clustering is … Read more

Statistics Definitions > Consistent Estimator What is a Consistent Estimator? A consistent estimate has insignificant errors (variations) as sample sizes grow larger. More specifically, the probability that those errors will vary by more than a given amount approaches zero as the sample size increases. In other words, the more data you collect, a consistent estimator … Read more

Regression Analysis > Hausman Test You may want to read this article first: What is an endogenous variable? What is the Hausman Test? The Hausman Test (also called the Hausman specification test) detects endogenous regressors (predictor variables) in a regression model. Endogenous variables have values that are determined by other variables in the system. Having … Read more

Regression Analysis > Model Misspecification What is Model Misspecification? Model Misspecification is where the model you made with regression analysis is in error. In other words, it doesn’t account for everything it should. Models that are misspecified can have biased coefficients and error terms, and tend to have biased parameter estimations. Left Out Variables Important … Read more