Asked by Beth
on 7 May 2013

Hi,

I am using the function anova2 to complete a two-way ANOVA. Here is the data:

d =

1.0e+03 *

0.0053 0.9991 0.0042 1.6223 0.0044 1.2638 0.0016 0.0031 0.0024 0.0036 0.0018 0.0036

Here is the code I ran:

[p,h,s]=anova2(d,3)

both columns and rows were significant with significant interaction:

p =

1.0e-04 *

0.9668 0.9543 0.9827

I ran multcompare on this analysis

[c, m, h, nms] = multcompare(s,'alpha',0.05,'ctype','bonferroni')

and this was my result:

c =

1.0000 2.0000 -854.1768 -645.9667 -437.7565

I realize that you can specify either column or row for the multcompare function, but shouldn't the multcompare function compare all quadrants:

i.e.

d =

1 2 3 4

Shouldn't the multcompare function compare 1 & 2, 1 & 3, 1 & 4, 2 & 3, 2 & 4 and 3 & 4, because both columns and rows were significantly different. Maybe I am misunderstanding how the multcompare function works.

Any help would be greatly appreciated. Thanks.

Beth

Answer by Tom Lane
on 10 May 2013

Accepted answer

You are right, it looks like multcompare with anova2 can only compare one dimension at a time. But multcompare with anovan can compare both. Try this:

row = [1 1 1 2 2 2 1 1 1 2 2 2]'; col = [1 1 1 1 1 1 2 2 2 2 2 2]'; [p,~,s] = anovan(d(:),{row col},'interaction') multcompare(s,'dim',1:2)

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