Glossary Terms Archive

Box-Cox Transformation: Formula, Lambda, and How Six Sigma Teams Use It

The Box-Cox transformation is a statistical method that converts non-normal data into a shape that closely resembles a normal distribution. Statisticians George Box and David Cox introduced it in a 1964 paper. Many statistical tools, including hypothesis tests and...

Bimodal Distribution: Definition, Causes, and What It Means for Six Sigma

A bimodal distribution is a probability distribution with two distinct peaks, separated by a valley. Each peak is called a mode — the value or range where data points concentrate most densely. When a histogram of process data shows two peaks, it is almost always...

Binomial Random Variable

The binomial random variable is simply the probability that a survey or experiment will succeed or fail multiple times. Binomials are a type distribution with two possible outcomes (the bi prefix means two or more). A coin toss...

Fault Tree Analysis (FTA)

Fault Tree Analysis (FTA) is a systematic, top-down method for analyzing the potential causes of system failures or accidents. It starts with a single undesirable event, known as the “top event,” and works downwards to identify all possible causes. This...

5S Methodology: Sort, Set in Order, Shine, Standardize, Sustain

5S is a Lean workplace organization method built around five sequential steps, each named for a Japanese word beginning with the sound “S”: Seiri, Seiton, Seiso, Seiketsu, and Shitsuke. In English, these translate to Sort, Set in Order, Shine, Standardize,...