00:01
So for this problem, we are given the two data sets of the average review for a group of 12 different stories if the story included the spoiler versus where it did not.
00:11
We're asked to find a 95 % confidence interval for the difference in mean enjoyment rating between the two stories.
00:17
So the first thing that i'll note is that for the version with the spoiler, which i'll label as mu s, or actually that should be x bar s, mean value there is about 6 .217.
00:33
And the standard deviation for the version with the...
00:37
Or, yeah, the standard deviation for the version with the spoilers is equal to 1 .22.
00:45
Then x bar for the original is equal to 5 .725.
00:51
The standard deviation for the original is equal to 1 .256.
00:59
So the way that we go about doing this is first we find what's called the pooled variance, which i'll label sp squared.
01:07
It's equal to n minus 1, where i'll note that's n for each one, or pardon me, it's going to be the number of individuals in each dataset minus 1.
01:18
There would be 15 or 15 in each group.
01:21
So we'd have 14 times s1 squared...