Statistics How To

Probability distributions > Loglinear model / distribution A log linear distribution (or loglinear model) is a discrete probability distribution that is typically used to analyze relationships between two or more categorical variables. When it is used to model cell counts in contingency tables, it is sometimes called a Poisson regression.  A logarithmic transformation is performed … Read more

Probability and Statistics > Markov’s Inequality gives an upper bound on the probability that a non negative random variable is greater than or equal to some positive constant. Given a non-negative random variable and a positive constant , Markov’s Inequality states that the probability that is greater than or equal to must be less than … Read more

A Two Proportion Z-Interval (or Z-Test) allows you to calculate the true difference in proportions of two independent groups to a given confidence interval. There are a few familiar conditions that need to be met for the Two Proportion Z-Interval to be valid. First, the groups must be independent. Subjects can be in one group … Read more

< Statistics definitions < Bivariate Correlation and Regression What is Bivariate Correlation? Bivariate correlation analyzes the relationship between two variables — usually two types of related data such as caloric intake and weight, income and house expenditures, or daily temperature and ice cream sales [1]. It tests whether the two variables have a linear relationship, … Read more

Effect Size > Glass’s delta Glass’s delta (Glass et al. 1981) is a measure of effect size. Glass’s delta uses only the control group’s standard deviation (SDC). This is because Glass argued that if several treatments were compared to a control group, it would be better to use just the standard deviation computed from the … Read more

Probability Distributions > The Edgeworth series distribution is a continuous probability distribution that approximates a probability distribution in terms of its cumulants and Hermite polynomials [1]. It relates the probability density function (PDF) to a standard normal distribution PDF. It is sometimes seen in statistical asymptotic theory, where approximations to sample statistic distributions of order … Read more

Probability Distributions > The Arfwedson distribution is a discrete probability distribution that was introduced by C. Arfwedson in 1951. It is a two-parameter distribution, with the parameters alpha and beta. The Arfwedson distribution is a special case of the occupancy distribution, and it can be used to model the number of different balls that have … Read more

Time Plot > Contents: Order of Integration (Time Series) Order of Integration (Integrals) Order of Integration (Time Series) You may want to read this article first: What is a Unit Root? “Order of integration” is a summary statistic used to describe a unit root process in time series analysis. Specifically, it tells you the minimum … Read more

Charts and Graphs > > Causal Graph What is a Causal Graph Model? A causal graph model (also called Bayesian networks, DAGs or path diagrams) are a way to represent how causality works in terms of what causes what. These probabilistic graphical models are used to encode assumptions about data-generating processes. Independence and conditional independence … Read more

Probability Distributions > What is the Beta Geometric Distribution? The Beta Geometric distribution is a unique type of distribution. We can think about it as being composed of two pieces: the probability that success will occur, and what’s known as shape parameters α and β which must always be positive numbers. This combination creates an … Read more