Mean is 120 and standard deviation of 15. Find percentage of people with readings between 114 and 126.

Question

 Have to use z-score table.

Answer 1

z = (x-μ)/σ  where x is the data point, μ is the mean (=120), and σ is the standard deviation (=15).

 

For x = 126:  z₁₂₆ = (126-120)/15 = ____?

For x = 114:  z₁₁₄ = (114-120)/15 = ____?

 

Go to a z-score table (http://www.z-table.com/) and read off the percentiles for the above z values.  The answer is:

 

(percentile for z₁₂₆) - (percentile for for z₁₁₄)