Page 198 - Intermediate Statistics for Dummies
P. 198
16_045206 ch10.qxd 2/1/07 10:14 AM Page 177
Chapter 10
Pairing Things Down with
In This Chapter
When and how to follow up ANOVA with multiple comparisons
Comparing two well-known multiple comparison procedures
Y Multiple Comparisons
ou’re comparing the means of not two, but k independent populations,
and you find out (using ANOVA — see Chapter 9) that you reject Ho: All
the population means are equal, and you conclude Ha: At least two of the
population means are different. Now you gotta know — which of those popu-
lations are different? Answering this question requires a follow-up procedure
to ANOVA called multiple comparisons, which makes sense because you want
to compare the multiple means you have and see which ones are different.
In this chapter, you figure out when you need to use a multiple comparison
procedure. You see two of the most well-known multiple comparison proce-
dures: Fisher’s LSD (least significant difference) and Tukey’s test. They can
help you answer that burning question: So some of the means are different,
but which ones are different?
Following Up after ANOVA
This section runs through the ANOVA procedure in the case where Ho is
rejected and leads you to the next step: multiple comparisons.
Suppose you want to compare the average number of cell-phone minutes
used per month for children and young adults, where the age groups are the
following:
Group 1: 19 years old and under
Group 2: 20-39 years old