   Six Sigma Glossary from MiC Quality
Measures of Dispersion
 Mean Square Deviation

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

See Mean Square Deviation

 Range

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

 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: RMSE

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

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

 Variance

A measure of the dispersion of a data set. The variance of a population is estimated from a sample using the formula: [SIX SIGMA GLOSSARY ALPHABETICAL INDEX] [SIX SIGMA GLOSSARY INDEX OF TOPICS] [Top]    