Question

Ms. Miller, the manager of a store, wants to find out what percent of all ​customers spend more than
$
50
$50 on a single visit.

​

​She randomly collects
35
35 ​receipts from last year.

​The rounded amounts, in dollars, are shown below.

​

​



​Part A:

Find the proportion of customers who spend more than
$
50
$50 on a ​single visit.


25
35​


​

​Part B:

Calculate the mean and standard deviation of the amount of money ​spent in a single visit (rounded to the nearest cent).

​ Mean ≈ $
56.91


​ Standard deviation ≈ $
16.72


​

​Part C:

Identify the range of amounts of money spent in a single visit within ​
2
2 standard deviations of the sample mean.

​

​Lower range = $
,

Upper range = ​$

Answer 1

Part A:
Proportion = 25/35 = 5/7 ≈ 0.7143 ≈ 71.43%.

Part B:
Given mean ≈ $56.91 and standard deviation ≈ $16.72.

Part C:
Within 2 standard deviations: mean ± 2·sd = 56.91 ± 2(16.72) = 56.91 ± 33.44.
Lower = $56.91 − $33.44 = $23.47
Upper = $56.91 + $33.44 = $90.35