Question

Given that a sample is approximately bell-shaped with a mean of 60 and a standard deviation of 3, the approximate percentage of data values that is expected to fall between 54 and 66 is

Answer 1

Use z-scores.
You will need to find the percentage of data values within two standard deviations from the mean. If you need to show this by hand, use the z-score formula.

Formula:

z = (x - mean)/sd

Find two z-scores, using 54 for x and also 66 for x. Mean = 60 and sd = 3.

Once you find the two z-scores, use a z-distribution table to determine your probability between the two z-scores.