[SIX SIGMA GLOSSARY ALPHABETICAL INDEX] [SIX SIGMA GLOSSARY INDEX OF TOPICS]

• Mean Square Deviation
• Mean Square Error
• Range
• Range Method
• RMSE
• Standard Deviation
• Variance

Refers to the mean of the squares of the deviations from the mean. It is equivalent to the Variance and is calculated from:

See Mean Square Deviation

The difference between the largest and smallest value in a subgroup. It can be used to estimate the process standard deviation, see Range Method.

A method for estimating the standard deviation used in Statistical Process Control and Measurement Systems Analysis. It uses the formula:

where 's' is the process standard deviation, and is the mean of more than 15 (preferably 30) samples, each containing an equal number of items. The constant d₂ is obtained from tables. If there are 15 samples, or less, then the formula is:

Root Mean Square Error, an alternative term for the standard deviation, calculated using the formula:

A measure of the dispersion of a data set. It can be calculated using the Range Method or the RMSE method.

A measure of the dispersion of a data set. The variance of a population is estimated from a sample using the formula: