00:01
So we are told that we have a normal distribution for a large set of test scores.
00:05
We are told that the mean is 500 and that the standard deviation is 100.
00:16
And then it says, or asks us what happens if every test score was increased by 25? how would that change the mean and the standard deviation? well, think about what the mean represents.
00:31
The mean represents the average of all of those test scores being added up together.
00:38
It's their actual values.
00:41
So if we increased all the test scores by 25 points, that would mean on average every single test score, right? because the mean is the average.
00:51
The mean is supposed to be making a comment about what's happening to all the test scores on average.
00:58
Well, if you do something to every single test score, of course that's going to change your mean.
01:03
That has to change the average.
01:05
And it's going to change it by exactly how much you add, meaning if you add 25, well, then the mean is going to change in the fact that it's going to be 25 higher.
01:17
Your mean will become 525.
01:21
Okay, that's guaranteed.
01:23
Here's the catch.
01:25
You have to understand what standard deviation means...