Lecture 42- ANOVA 2

Question 1

What might be a reason why a researcher fails to get a significant result (p value) in an ANOVA despite having been pretty confident?

Answer 1

Because true differences in group means was lost in amongst noise

Question 2

How can the problem of excess noise be managed?

Answer 2

By the technique of blocking. This variable is introduced to soak up residual variation in the data so as to allow effects of interest to be more easily investigated.

Question 3

Calculate the F statistic from the ANOVA table on slide 810…

Answer 3

1.0242

Question 4

Find the p value using r shown on slide 812

+ Make a conclusion

Answer 4

Look at slides for r code and answer

Question 5

What happens in an ANOVA if the difference between means is large? What can be done to solve this?

Answer 5

• Large Residual sum of square
• Means that even if the GMS is large the F statistic may not appear extreme

-To solve engage in the blocking technique (remove the effect of differences in the groups from RSS)

Question 6

Once we have engaged in blocking what do we expect to happen to the F statistic?

Answer 6

Expect it to be higher than before, then resulting p stat will plummet