In the Oneway platform, analysis of means (ANOM) is a multiple comparison method for means or variances. Each ANOM report contains a decision chart with the following elements:
• an upper decision limit (UDL)
• a lower decision limit (LDL)
• a horizontal (center) line; the center line position is determined by the chart type:
– ANOM: the overall mean
– ANOM with Transformed Ranks: the overall mean of the transformed ranks
– ANOM for Variances: the root mean square error (or MSE when in variance scale)
– ANOM for Variances with Levene (ADM): the overall absolute deviation from the mean
– ANOM for Ranges: the mean of the group ranges
If a group’s plotted statistic falls outside of the decision limits, then the test indicates that there is a statistical difference between that group’s statistic and the overall average of the statistic for all the groups.
In the Oneway platform, each Analysis of Means red triangle menu contains the following options:
Set Alpha Level
Enables you to select a significance level from the list or specify a level with the Other selection. The upper and lower decision limits update when the alpha level changes.
Note: For ANOM for Ranges, only the significance levels of 0.10, 0.05, and 0.01 are available.
Show Summary Report
Shows or hides a summary report that is based on the Analysis of Means method:
– For ANOM, creates a report showing group means and decision limits.
– For ANOM with Transformed Ranks, creates a report showing group mean transformed ranks and decision limits.
– For ANOM for Variances, creates a report showing group standard deviations (or variances) and decision limits.
– For ANOM for Variances with Levene (ADM), creates a report showing group mean ADMs and decision limits.
– For ANOM for Ranges, creates a report showing group ranges and decision limits.
Graph in Variance Scale
(Available only for the ANOM for Variances option.) Changes the scale of the vertical axis in the decision chart between either standard deviations units or variances.
Display Options
Contains the following options to customize the display:
Show Decision Limits
Shows or hides decision limit lines.
Show Decision Limit Shading
Shows or hides decision limit shading.
Show Center Line
Shows or hides the center line statistic.
Point Options: Show Needles
Shows the needles. This is the default option. The Show Connected Points option shows a line connecting the means for each group. The Show Only Points option shows only the points representing the means for each group.
Unlike the other ANOM decision limits, the decision limits for the ANOM for Ranges chart uses tabled critical values. For this reason, ANOM for Ranges is available only under the following conditions:
• groups of equal sizes
• groups specifically of the following sizes: 2–10, 12, 15, and 20
• number of groups between 2 and 30
• alpha levels of 0.10, 0.05, and 0.01