# Thread: How do you know when to reject a null hypothesis in an ANOVA?

1. ## How do you know when to reject a null hypothesis in an ANOVA?

The problem is basically that smaller birds with smaller brains migrate to warmer weather in the winter because they don't know how to find food, but bigger birds with bigger brains don't migrate because they know how to find food.

So I did all the work right I'm just always confused whether I should reject or fail to reject and the sentence that comes after. So I have...
the critical F region is F=3.68
then when I calculated it F= 19.30
So do I reject the null hypothesis because it doesn't fall in the critical region? I'm not exactly sure what that means. My teacher has us do drawings so if it's to the right of the shaded part do I reject? Then the sentence that comes after would I say...

Reject Ho. Brain size in a bird does not affect migration in the winter.

I think I have it backwards though.

2. ## Re: How do you know when to reject a null hypothesis in an ANOVA?

i think you're talking yourself into confusion with your first sentence.

the critical F region is F=3.68
this isn't a region, it is a point. The critical region will be $F \geq 3.68$

So your result is inside the critical region. Lookup the definition of critical region and then you will know whether or not to reject your hypothesis.

Spoiler:

From wikipedia:
"The critical region of a hypothesis test is the set of all outcomes which cause the null hypothesis to be rejected in favor of the alternative hypothesis. "