00:01
So in this question letter a, we should find here, assuming that we have a bell shape, which basically means that we have this, and the middle here is the mean.
00:11
And we can find some points according to what we call the empirical rule.
00:18
So the points that we have is one standard deviation below the mean, so 35 minus 6, which is 23.
00:28
We can find 35 minus, oh, sorry.
00:31
This is 2.
00:32
Let me add another one, and another one.
00:35
So we have 3.
00:37
So for example, the first one is, like i said, is like 35 minus 6, which is 29.
00:44
Then we have, if you subtract another 6, you have 23.
00:48
And if you subtract another 6, you have 17.
00:51
And if you do the same thing for the other side, you have 41, then 47, and then 53.
01:00
So now what we have, because we have the bell shape, is that the area that we have here, which is within one standard deviation, is 68 % of the observations.
01:11
We have here 95, and we have here 99.
01:17
So in the first part of this question, you're interested in the 95%.
01:21
So using the empirical rule, we know that the values will be between 23 and 47.
01:28
So we don't need to do any other calculation.
01:30
Then for letter b, we are interested in the percentage of values that are between 17, so this value, and 47, which is this...