Basic Analysis and Graphing - SAS

54 Performing Univariate Analysis Chapter 2
Options for Continuous Variables
Related Information
• “Statistical Details for Prediction Intervals” on page 72
• “Example of Prediction Intervals” on page 64
Tolerance Intervals
A tolerance interval contains at least a specified proportion of the population. It is a confidence interval for
a specified proportion of the population, not the mean, or standard deviation. Complete discussions of
tolerance intervals are found in Hahn and Meeker (1991) and in Tamhane and Dunlop (2000).
When you select the Tolerance Interval option for a variable, the Tolerance Intervals window appears. Use
the window to specify the confidence level, the proportion to cover, and either a one-sided or two-sided
limit. The calculations are based on the assumption that the given sample is selected randomly from a
normal distribution.
Related Information
• “Statistical Details for Tolerance Intervals” on page 72
• “Example of Tolerance Intervals” on page 66
Capability Analysis
The Capability Analysis option measures the conformance of a process to given specification limits. When
you select the Capability Analysis option for a variable, the Capability Analysis window appears. Use the
window to enter specification limits, distribution type, and information about sigma.
Note: To save the specification limits to the data table as a column property, select Save > Spec Limits.
When you repeat the capability analysis, the saved specification limits are automatically retrieved.
The Capability Analysis report is organized into two sections: Capability Analysis and the distribution type
(Long Term Sigma, Specified Sigma, and so on).
Capability Analysis Descriptions
The Capability Analysis window, report, and options are described in the following tables.
Table 2.13 Description of the Capability Analysis Window
By default, the normal distribution is assumed when calculating the
capability statistics and the percent out of the specification limits. To
perform a capability analysis on non-normal distributions, see the
description of Spec Limits under “Fit Distribution Options” on
page 58.