00:01
We are looking at a normal distribution, so i'm going to start by drawing it.
00:08
So the area under this curve is one, it's a probability curve, and it's symmetric.
00:14
So half of charges, 50%, or 0 .5, will be below the mean, half above the mean.
00:21
Mean mu is 15%, standard deviation is 4%.
00:27
So mu and sigma there.
00:28
And i'm using percent as units, so i've dropped from there.
00:32
I just need to know that if i'm going back to raw values, i include the units.
00:38
Okay, so what must the aprb to be in the bottom at 10%.
00:44
So that will be down here somewhere.
00:46
I can call that p10th percentile, and i know that 10 % charge less.
00:53
This little area here is 10%, 0 .1.
00:56
Everything else is 0 .9, 90%...