I have not used ANOVA much since school, at least beyond one-way, but I
recently started to read up on it and play around with it and Excel. One
book I've looked at is the 3rd edition of Elementary Statistics by Bluman.
They have an example problem on two-way ANOVA that I'm stuck on. (It's on
page 567)
This is a simple 2x2 two-way ANOVA problem with the following data:
Two Wheel Four-Wheel
Regular 27.6 28.6
25.2 29.3
High 32.8 24.2
32.8 24.2
It does not matter, but this is gas mileage for two and four wheel drive on
regular and "high test". They show the following ANOVA table:
Source SS df
--------------------------------
Gasoline, A 3,920 1
Automobile, B 9,680 1
Interaction (AxB) 54,080 1
Within (error) 3,300 4
--------------------------------
Total 70,880 7
The rest is calculated based on this so I will not bother to key it in from
the textbook.
Excel does not offer two-way ANOVA but it does offer two-factor ANOVA with
replication. I as assuming that two-way = two-factor and that seems to
match problems in other books I've looked at. With Excel, I get the following:
Source SS df MS F P-value F crit
Sample 1.361 1 1.361 1.742 0.257 7.709
Columns 18.301 1 18.301 23.426 0.008 7.709
Interaction 62.161 1 62.161 79.566 0.001 7.709
Within 3.125 4 0.781
Total 84.949 7
I don't think the differences between Bluman and Excel are due to any
problems with Excel since it gets the right results with problems I tried
from other textbooks. Any ideas on what I, Bluman, or Excel is doing wrong
or differently?
I was also going to try this problem in SPSS 9 but it only has a One-Way
ANOVA option on the Compare Means menu so I guess I don't have the right
module.
Ronny Richardson
.
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