Means table for Analyze Variability

Interpretation

Use the Means table to understand the statistically significant differences between the factor levels. The value of each factor level provides an estimate of the log of each population standard deviation. Look for differences between factor level standard deviations for terms that are statistically significant.

For main effects, the table displays the groups within each factor and their log standard deviations. For interaction effects, the table displays all factor level combinations. If an interaction term is statistically significant, do not interpret the main effects without considering the interaction effects.

In these results, the Means table shows how the strength of insulation varies by material, injection pressure, injection temperature, and cooling temperature. Material is the only factor that is statistically significant at the 0.05 level. However, the interaction between Material and InjPress is also statistically significant at the 0.05 level, so do not interpret the Material main effect without considering the interaction effect.

For the interaction of material by injection pressure, the standard deviation of strength (0.4840) is lower when formula 2 is used and injection pressure is set at 150. For the material, the standard deviation of strength is lower when formula 2 (0.8716) is used than when formula 1 (2.2757) is used.

Interpretation

Use the standard error of the mean to determine how precisely the fitted value estimates the log of the standard deviation.

A smaller value of the standard error of the mean indicates a more precise estimate of the standard deviation. A larger sample size results in a smaller standard error of the mean and a more precise estimate of the standard deviation.