Reporting an ANOVA
What are those numbers in the parentheses in the APA
Manual??
- Both of them are degrees of
freedom - the degrees of freedom for the "F-ratio."
- The top number is for the issue
being addressed (that is a Main Effect or an Interaction).
- The bottom number is for the
Error Term (look for it, and the othere "df"s on your output.
Let's say you have a 2 (Sex) x 2 (Political Party)
ANOVA
that looks at body weight:
-
You owe the reader 3 F statistics (formatted
following the
APA Manual)
-
one each for the Sex and Political Party Main
Effects
-
one for the Interaction between these two
variables.
-
You owe the reader a set of Descriptive Statistics (n,
mean, and SD) for each group involved in the preceding Fs. That
is,
2 sets for each of the Main Effects and 4 sets for the 2 x 2
Interaction
(a total of 8 sets). I'll accept a figure to replace all
descriptives
for the Interaction.
As your ANOVA gets bigger, your F and Descriptive
Statistics
obligations grow. Considering Descriptive Statistics only, for
example:
-
2 x 5
-
7 sets for the Main Effects (clusters of 2 and 5)
-
10 sets for the Interaction
-
2 x 2 x 2 (Think of the variables as being A, B,
and C)
-
6 sets for the Main Effects (clusters of 2, 2,
and 2)
-
12 sets for the 2-Way Interactions (4 for A-B, 4
for A-C,
and 4 for B-C)
-
8 sets for the 3-Way Interaction (A-B-C)
Lots of numbers with complex designs, eh? I try
to
avoid 3 (or more) way analyses--simplify! |