In an earlier segment, you devised the null and alternate hypothesis as follows
H0:p=0.4
Ha:p≠0.4
Now, let’s change the hypothesis statement slightly. Let’s say the claim was made that the Search CTR is actually equal to or more than 40%. How would that change the hypothesis? And does the decision change in this case? Let’s take a look at the next video to find out.
[Note: The Prof says “greater than 40%” instead of “equal to or greater than” 40% at 0:09. The alternate hypothesis is considered less than 40% therefore the null hypothesis should be greater than equal to 40%.]
Thus as you saw, the new null and alternate hypotheses came out to be
Ho:p≥0.4
Ha:p<0.4
This changed the entire hypothesis test from a two-tailed test to a one-tailed test. Therefore, when you computed the p-value you only took into consideration one tail and that value came out to be 0.0395. In the critical value terms as well, the necessary critical region only consists of 0.0395 area. Since it is less than the value of 0.05, you need to reject the null hypothesis in this case.