00:01
In this question, we are looking at a normal distribution, so i'll start by drawing it.
00:08
The total area under this curve is 1 or 100%, and it is symmetric, so half will be below the mean, half above the mean.
00:18
For part a, we want to know what percentage of men meet height requirements to play characters at an amusement park.
00:25
So we're looking at the distribution of male heights.
00:28
M is 67 .4, sigma, a standard deviation, is 3 .6 .6 .6 .6 .6.
00:34
We're looking at between 57 and 62.
00:38
Both of those values are below the mean.
00:40
So i'm mark from on here.
00:41
We want to know what percentage of men fall into this interval.
00:46
So the first thing we do is find the corresponding z scores.
00:50
Z is x minus mu over sigma.
00:56
So we want 57 minus 67 .4, so that's minus 10 .4, divided by 3 .7, and 62 minus 67 .4.
01:06
And it's 5 .4, divided by 3 .7.
01:10
This tells us how many standard deviations away from the mean these values are.
01:15
And the first one is about minus 1 .46, the second about minus 2 .81.
01:21
But i want to use the exact values to maintain accuracy.
01:24
My next step is to turn these z scores into areas under the curve.
01:29
And i have two tools at my disposal.
01:31
They are the standard normal and the cumulative normal functions.
01:35
Standard normal gives you the area between x and mu.
01:42
So if i put in this one, it would give me this area here in red.
01:47
If i put in this one, it would give me red plus green.
01:51
Red plus green minus red leaves me my interval.
01:55
Cumulative is the area to the left.
01:59
So very similar, except the more negative score would give you red and the less negative would give you red plus green.
02:06
I'll use for standard.
02:07
So for red plus green, i'm putting this minus 10 .4 over 3 .7 into the standard normal function on my calculator.
02:23
You can also find it on excel or r.
02:25
I get 0 .4 .9753...