What conclusion can be drawn if we do a t-test which results in a p-value of 0.0012?

Question

A researcher did a t-test which results in a p-value of 0.0012; what, if any, conclusion can be drawn given the information provided?

A:The 95% confidence interval for the differences between the mean will exclude the observed difference

B:The 99% confidence interval for the differences between the mean will include the observed difference

C: The result is significant and the effect size is going to be large

D: The result is significant

E: The effect size is going to be large

Answer 1

A 95% confidence interval corresponds to 2.5% in each of the two tails of a normal distribution. This is a p-value of 0.025. A 99% confidence interval similarly corresponds to a p-value of 0.005.

An experimental p-value of 0.0012 is below the critical values for both a 95% and a 99% CI. So the experimental result lies outside what would be expected by random chance, and the result is significant. It usually implies rejecting the null hypothesis in favour of the alternative hypothesis. 

I think options A and D apply.

Comments

Hello Rod, thank you for your help as always.