Glossary Terms Archive

Confounding

Confounding is a crucial concept in research. It describes a situation where a third variable influences both the independent and dependent variables. This creates a spurious association. It makes it seem like the independent variable is causing the dependent...

Confidence Interval in Six Sigma: A Plain-Language Guide

You measure a sample of parts and find the average diameter is 10.2mm. But how reliable is that number? Does it describe the whole process, or just the 30 parts you happened to measure? This is exactly the problem a confidence interval solves. A confidence interval...

Coefficient of Determination (R²): What It Really Tells You

The coefficient of determination, written R² and read “R-squared,” is the proportion of variation in an output (Y) that a regression model explains using its input variable(s), expressed as a value between 0 and 1, or 0% to 100%. An R² of 0.75 means the...

Chi-Square Test: Definition, Examples, and How to Use It in Six Sigma

A chi-square test is a statistical hypothesis test used to determine whether observed counts in categorical data differ significantly from what would be expected by chance. It comes in two forms that get confused constantly: a goodness of fit test, which checks...

Chi-Square Distribution: Shape, Degrees of Freedom, and Why It Matters

The chi-square distribution is a continuous probability distribution formed by summing the squares of independent standard normal random variables, and it is the reference distribution behind every chi-square test result. Unlike the normal distribution, it can...