Use the 68-95-99.7 rule to solve the problem. - The amount of Jen's monthly phone bill is normally distributed with a mean of $53 and a standard deviation of $11. What percentage of her phone bills are between $20 and $86?

Question

Use the 68-95-99.7 rule to solve the problem. - The amount of Jen's monthly phone bill is normally distributed with a mean of $53 and a standard deviation of $11.  What percentage of her phone bills are between $20 and $86?

PsyDAG · Answer

Z = (score-mean)/SD

Z = (20-53)/11 = -33/11 = -3

Calculate the other Z score and use the rule to calculate percentage between the two. Remember that the rules apply in both directions.

Or you could use a table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.

victor · Answer

99.7