Absolute Correlations
In the Compare Designs report, the Absolute Correlations section summarizes information about correlations between model terms and alias terms.
Absolute Correlations Table
The table in the Absolute Correlations report is divided into three sections:
• Model x Model considers correlations between terms corresponding to effects in the Model list.
• Model x Alias considers correlations between terms corresponding to effects in the Model list and terms corresponding to effects in the Alias list.
• Alias x Alias considers correlations between terms corresponding to effects in the Alias list.
Note: If there are no alias terms, only the Model x Model section appears.
For each section of the report, the following are given:
Average Correlation
The average of the correlations for all pairs of terms considered in this section of the report.
Number of Confoundings
The number of pairs of terms consisting of confounded terms.
Number of Terms
The total number of pairs of terms considered in this section of the report.
The values in the Absolute Correlations table are colored according to a color gradient shown under the table. You can control the color legend using the options in the Absolute Correlations red triangle menu. See Color Legend.
Figure 17.18 Absolute Correlations Report for Three Designs
Color Map on Correlations
The Color Map on Correlations section shows plots for each of the designs. The cells of the color map are identified above the map. There are cells for all terms that correspond to effects that appear in either the Model section or the Alias Terms section. Each cell is colored according to the absolute value of the correlation between the two terms.
By default, the absolute magnitudes of the correlations are represented by a white to gray to black intensity color theme. In general terms, the color map for a good design shows a lot of white off the diagonal, indicating orthogonality or small correlations between distinct terms. Large absolute correlations among effects inflate the standard errors of estimates.
To see the absolute value of the correlation between two effects, hover over the corresponding cell. For a custom color scale, right-click in the plot and select Color Theme. To save a table of the correlations, right-click to the right of the plot below the legend and select Table of Correlations.
Figure 17.19 Color Map on Correlations Report for Three Designs
