# If the difference in means doesn't fall in the 95% CI but 0 does, what to do?

A question regarding bootstrap confidence intervals. If the hypothesis is comparing two means (e.g. the difference in calorie intake between males and females), should the value 0 be used or the difference in means be used to refer to at the end when we compare it to the 95% confidence interval.

In my instance the difference in mean ($\bar{x_1}$ - $\bar{x_2}$) did not fall in the 95% confidence interval. Suppose the value 0 (since the hypothesis is $\bar{x_1}$ - $\bar{x_2}$ = 0) lies within the 95% confidence interval.

Should we reject the null hypothesis?

• It's very strange that the difference of your two samples doesn't fall in the confidence interval for the difference. Are you sure about it? As @grldsndrs said, I'm afraid you might have get confused with different differences or intervals.
– Pere
Oct 26 '16 at 10:19