Question

What is the 75th percentile of the adhesion distribution?
A locomotive's 'adhesion' is the locomotive's pulling force as a multiple of its weight. A diesel locomotive model has adhesion which varies in actual use according to a Normal distribution with a mean .037 and a variance of 0.0016.

Can someone tell me how to do this problem thanks

Answer 1

Use a z-score formula:

z = (x - mean)/sd

z = value from a z-table corresponding to the 75th percentile
x = the value you are trying to find
mean = .037
sd = square root of the variance 0.0016

Once you have the values plugged into the formula, solve for x.