# Long Tail Distribution: Simple Definition

Probability Distributions > A long tail distribution has tails that taper off gradually rather than drop off sharply. They are a subset of heavy-tailed distributions. It’s easy to visualize the idea of a long tailed function, and slightly harder to…

# Nonnormative Influences

Confounding Variables > Nonnormative influences are influences which don’t influence every member of a set in the same way. The term normative refers to something that affects everyone in a culture at the same time, so nonnormative implies it affects…

# Likelihood Function: Overview / Simple Definition

Statistics Definitions > Many probability distributions have unknown parameters; We estimate these unknowns using sample data. The Likelihood function gives us an idea of how well the data summarizes these parameters. The “parameters” here aren’t population parameters— they are the…

Confounding Variables > Normative age graded influences are influences that affect an individual in a predictable or semi-predictable way according to age. The word normative here means that they are ‘the norm’ for a large number of people in a…

# Lévy Distribution: Definition, PDF, Examples

Probability Distributions The Lévy Distribution is a probability distribution that is both continuous—for non-negative random variables—and stable. To be stable means that if you sum up random variables x and y in a distribution, their sum (i.e. x + y)…

# Log Odds: Simple Definition & Examples, Conversions

Logistic Regression > Log odds play a central role in logistic regression. Every probability can be easily converted to log odds, by finding the odds ratio and taking the logarithm. Despite the relatively simple conversion, log odds can be a…

# Gibbs Sampling: Definition & Overview

Markov Chain Monte Carlo > Gibbs Sampling What is Gibbs Sampling? Gibbs sampling (also called alternating conditional sampling) is a Markov Chain Monte Carlo algorithm for high-dimensional data such as image processing and micro arrays. It is called Monte Carlo…

# Midpoint / Class Mark (in Statistics)

Statistics Definitions > You may want to read this article first: What is a Bin? The class midpoint (or class mark) is a specific point in the center of the bins (categories) in a frequency distribution table; It’s also the…

# Infinite Variance

Probability Distributions > What is Infinite Variance? Variance is a measure of how spread out a distribution is. Distributions with infinite variance have fat upper tails that decrease at an extremely slow rate. Intuitively, this means that the distribution will…

# Fat Tail Distribution: Definition, Examples

Probability Distributions > What is a Fat Tail Distribution? The term “fat tail” distribution has more than one definition, depending on where you read about it. Part of the problem is that there’s no universal definition for the term tail…