During this time there were a total of 67 new subscriptions. Of these 58% (39) came from the new design and 42% (28) came from the old design. Looks like the new one is a clear winner. Is it? This seems a small population to settle on a clear winner. Using R's prop test, I get a p value of 0.22. (Type "prop.test(39,67)" to calculate it). I think this means that in a world where it makes no difference which design is…
That's not how you use prop.test. What you've tested using that invocation is the null hypothesis that the underlying probability of 39/67 is 0.5. If you want to perform a test of a difference of two proportions, you need to do: prop.test(c(39, 67), c(total_group_a_impressions, total_group_b_impressions)) I don't have experience with A/B testing, so I'm not sure if this is typically or best handled using this particu…
What you've tested using that invocation is the
null hypothesis that the underlying probability
of 39/67 is 0.5.
Isn't that equivalent to my interpretation of the test result? "In a world where it makes no difference which design is used, you would get a result as significant as this 22% of the time". If you want to perform a test of a difference of two proportions, you need to do:
prop.test(c(39, 67), c(total_group_a_impressions, total_group_b_impressions))
Do you mean c(39,28)? Because group_a had 39 hits and group_b hat 28. Doing so with the group sizes Bemmu stated (3000/3000) also gives me a p value of 0.22.As long as the group sizes are equal, the test is not very sensitive to the sizes.