Exercise

# Exercise 2. Averages and Standard Deviations

Suppose all you know about the height data from the previous exercise is the average and the standard deviation and that its distribution is approximated by the normal distribution. We can compute the average and standard deviation like this:

```
library(dslabs)
data(heights)
x <- heights$height[heights$sex=="Male"]
avg <- mean(x)
stdev <- sd(x)
```

Suppose you only have `avg`

and `stdev`

below, but no access to `x`

, can you approximate the proportion of the data that is between 69 and 72 inches?

Given a normal distribution with a mean `mu`

and standard deviation `sigma`

, you can calculate the proportion of observations less than or equal to a certain `value`

with `pnorm(value, mu, sigma)`

. Notice that this is the CDF for the normal distribution. We will learn much more about `pnorm`

later in the course series, but you can also learn more now with `?pnorm`

.

Instructions

**100 XP**

- Use the normal approximation to estimate the proportion the proportion of the data that is between 69 and 72 inches.
- Note that you can't use
`x`

in your code, only`avg`

and`stdev`

. Also note that R has a function that may prove very helpful here - check out the`pnorm`

function (and remember that you can get help by using`?pnorm`

).