Statistics Definitions > 68 95 99.7 rule Contents: Empirical Rule (68 95 99.7 rule) Empirical Research What is the 68 95 99.7 rule? Watch the video or read on below: When you use a standard normal distribution (aka Gaussian Distribution):…

## Measurement Variable: Definition, Examples

Types of Variables > Simply put, a measurement variable (sometimes called a numeric variable) expresses some type of measurement and has a number associated with it. For example: 12 cm, 5 feet, or 310 meters. The measured quantity doesn’t have…

## Quadratic Mean / Root Mean Square

Descriptive Statistics > Quadratic Mean / Root Mean Square What is the Quadratic Mean / Root Mean Square? The quadratic mean (also called the root mean square*) is a type of average. It measures the absolute magnitude of a set…

## Quartic Regression

Regression Analysis > Quartic regression fits a quartic function (a polynomial function with degree 4) to a set of data. Quartic functions have the form: f(x) = ax4 + bx3 + cx2 + dx + e. For example: f(x) =…

## Continuous Sample Space: Simple Definition, Examples

Statistics Definitions > Sample spaces introduced in early probability classes are typically discrete. That is, they are made up of a finite (fixed) amount of numbers. For example, if you roll a die, the sample space (Ω) is [1, 2,…

## Shannon Entropy

Statistics Definitions > Shannon entropy (or just entropy) is a measure of uncertainty (or variability) associated with random variables. It was originally developed to weigh the evenness and richness of animal and plant species (Shannon, 1948). It’s use has expanded…

## Natural Number: Definition and Examples

Statistics Definitions > Natural Numbers and Whole Numbers Contents (Click to skip to that section) Natural Number Whole Numbers Why Is a Natural Number a Whole Number? Whole Numbers Example Closed Sets and Wholes Properties of Whole numbers What is…

## Independence of Irrelevant Alternatives

Statistics Definitions > What is Independence of Irrelevant Alternatives? Independence of Irrelevant Alternatives (IIA) is a condition that states that the relative likelihood of choosing from A from B won’t change if a third choice is placed into the mix.…

## Additive Model & Multiplicative Model

Regression Analysis > Additive Model and Multiplicative Model in Regression The additive model and multiplicative model are generalizations of the “usual” linear regression model (Hastie & Tibshirani, 1990). The additive model is the arithmetic sum of the predictor variables‘ individual…

## Prior Distribution: Simple Definition, Example

Bayesian Statistics and Probability > A prior distribution represents your belief about the true value of a parameter. It’s your “best guess.” One you’ve done a few observations, you recalculate with new evidence to get the posterior distribution. Formally, the…