Use the empirical rule to solve the problem.
-The amount of Jen's monthly phone bill has a roughly bell-shaped distribution with a mean of $57 and a standard deviation of $9. What percentage of her phone bills are between $30 and $84?
A)99.7%
B)95%
C)99.99%
D)68%

Question

Use the empirical rule to solve the problem.
-The amount of Jen's monthly phone bill has a roughly bell-shaped distribution with a mean of $57 and a standard deviation of $9. What percentage of her phone bills are between $30 and $84? 
A)99.7%
B)95%
C)99.99%
D)68%

Quizplus · Accepted Answer

The empirical rule states that for a bell-shaped distribution, approximately 68% of the data falls within one standard deviation of the mean, 95% within two standard deviations, and 99.7% within three standard deviations. Here, $30 to $84 is $27 below and above the mean ($57), which is three standard deviations ($9 x 3 = $27). Therefore, about 99.7% of her phone bills fall within this range.

Use the Empirical Rule to Solve the Problem