Chi-square test for biology (divide by 0)?

Question

Ok, so this is for biology, and we are doing the chi-square test for a lab where we saw if pill bugs preferred wet or moist environments.

Our expected amounts for the dry dish was 0, so when I try to do the calculations, It doesn't work. What do I do?

((O-E))^2/E

Answer 1

Hi there, you want to make your chi square assume that the pill bugs have NO preference for any area.  So if they didn't prefer wet or dry, then half the bugs would go to each area.

So make your expected as if half of the bugs were in each area.

Then if your chi-square value turns out to be significant, you can reject your NULL hypothesis that there is no preference, and instead you conclude there IS a preference.