Fisher's LSD method compares the means for each pair of factor levels using the individual error rate you select. Note that the family error rate, which is the probability of making one or more type I errors for the entire set of comparisons, will be higher than the error rate for each individual comparison.

The grouping information table highlights the significant and nonsignificant comparisons. The table includes the following information.

·    Method – the multiple comparison method used to construct the family of confidence intervals from which the grouping table is generated.

·    Comparison term – each grouping information table compares levels of one factor.

·    N – the sample size for each factor level.

·    Mean – fitted means sorted in descending order.

·    Grouping – contains columns of letters that group the factor levels. Levels that share a letter are not significantly different. Conversely, if they do not share a letter, the level means are significantly different.

To determine a likely range for the difference between two means, use the interval plot for differences of means.

The grouping information for the paint hardness data shows that group A contains Blends 1 and 4; group B contains Blends 1 and 3; and, group C contains Blends 2 and 3. Blends 1 and 3 are in two groups. Factor levels within a group are not significantly different from each other. Because the following factor level combinations do not share a letter, their means are significantly different:

·    Blend 1 and 2

·    Blend 2 and 4

·    Blend 3 and 4