Question

Monthly sale figures for a particular e-retailer tend to be normally distributed with mean equal to 150
thousand dollars and a standard deviation of 35 thousand dollars. Use the normal distribution to compute the
values (you can use the applets listed in lecture 2 notes or the Excel function). Show your work.
a) What percentage of monthly sales is less than 200 thousand dollars? [2 points]
b) What’s the top 1% monthly sale figure (a.k.a. 99th percentile)? [2 points]
c) What percentage of monthly sale values is between 200 and 250 thousand dollars? [2 points]
d) What percentage of monthly sales are above 180 thousand dollars? [2 points]

Answer 1

Here it is given that distribution is normal with mean=150 and standard deviation=35

a. Here we need to find

As distribution is normal we can convert x to z

b. Here we need to find x such that or

Using z table we get

So

Hence

c.

d.

So are the answers