General MANOVA

Univariate Statistics - ANOVA Table for Quality

  

When you do a general MANOVA, you can choose to calculate the univariate statistics to examine the individual responses.

The most important statistic in the analysis of variance table is the p-value (P), which exists for each term in the model (except for the error term). The p-value for a term tells you whether the effect for that term is significant:

·    If P is less than or equal to the a-level you selected, then the effect for the term is significant.

·    If P is larger than the a-level you selected, the effect is not significant.

If a factor is significant, the level means for the factor are significantly different from each other.

If an interaction term is significant, the effects of each factor are different at each level of the other factors. For this reason, you should not analyze the individual effects of terms involved in significant higher-order interactions.

Example Output

Analysis of Variance for Quality, using Adjusted SS for Tests

 

Source         DF   Seq SS  Adj SS  Adj MS    F      P 

Method          1   8.859   9.220   9.220  7.53  0.008

Plant           2   6.763   7.057   3.529  2.88  0.064

Method*Plant    2   0.707   0.707   0.354  0.29  0.750

Error          56  68.590  68.590   1.225

Total          61  84.919

Interpretation

In the door lock analysis, you assessed the effects of method, plant, and the method- by-plant interaction for the quality response. Assuming that you chose the common a-level of 0.05 for the test, the results indicate that:

·    The p-value for the interaction term (0.750) is greater than 0.05. Thus, the interaction is not significant, and you can consider the effects of the method and quality separately.

·    The p-value for the method factor is 0.008. Because this value is less than the chosen a-level of 0.05, the effect of method on quality is significant. In other words, the mean quality score is different for the two production methods.

·    The p-value for degree is greater than 0.05 (0.064), indicating that there is no significant effect of plant location on quality.