The distribution of hourly sales for a local family owned store is normally distributed with a mean of $225 per hour and a standard deviation of $75 per hour. Which of the following intervals contains the middle 95% of hourly sales

The standard deviation of 75 dollars

Explanation:

Standard deviation, S. D. = 75 dollars; Mean, M = 225 dollars; Mean deviation, D=?

S. D. = √ D² - M

∴ 75 = √ D² - 225

D² = 75² - 225 = 5625 + 225 = 5950

∴ D = √5950 = 24.4 dollars

From the above, it shows that, the standard deviation of 75 dollars contains the middle 95 percent of hourly sales.