2
$\begingroup$

I have ran a nested ANOVA on a data set and the results suggest that there is an association for the higher level with an insignificant P-value but also an association for the lower level with a significant P-value. Is this even possible, or have I done something completely wrong?

Details

I have a data set comprising of: Groups (A,B,C...) - each group contains 3 different genotypes (1,2,3...). The same genotype doesn't occur in two different groups. For example, I have group A with genotypes 1,2,3 and Group B with genotypes 4,5,6, and group C with genotypes 7,8,9. I then have several measurements of height for each genotype. I had to perform an analysis that can test for differences between the three groups as well as for the genotypes within each of the groups. I chose nested ANOVA, but now I'm slightly doubting myself. A huge thank you for any help!

$\endgroup$
  • $\begingroup$ Basically I have a data set comprising of: Groups (A,B,C...) - each group contains 3 different genotypes (1,2,3,..). The same genotype doesn't occur in two different groups. I then have several measurements of height for each genotype. I had to perform an analysis that can test for differences between the three groups as well as for the genotypes within each of the groups. I chose nested ANOVA, but now I'm slightly doubting myself. A huge thank you for any help! $\endgroup$ – sshelp Nov 26 '12 at 11:50
  • $\begingroup$ Sorry, I didn't make it quite clear: I have group A with genotypes 1,2,3 and Group B with genotypes 4,5,6, and group C with genotypes 7,8,9. $\endgroup$ – sshelp Nov 26 '12 at 16:56
  • $\begingroup$ you can delete these comments now... I edited the question because I don't think you can with your reputation. Now that we have details, do you mean groups is the higher level and genotypes is the lower level? $\endgroup$ – John Nov 26 '12 at 17:06
2
$\begingroup$

This can happen a number of ways. You need to examine your outcome variables to see what happens but imagine something like the following.

height group gene
200    A     1
150    A     2
150    A     3
200    B     4
150    B     5
150    B     6

It's easy to see how gene's 1 and 4 lead to greater heights but there's no difference between the groups.

| cite | improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.