# Thread: Standard Deviation Help needed!

1. ## Standard Deviation Help needed!

I'm really stumped by this question since the 1st standard deviation would be 0.41, not 0.40. . .

An important measure of the performance of a locomotive is it's "adhesion" which is the locomotive's pulling force as a multiple of it's weight. The adhesion of one 4400-horsepower diesel locomotive model varies in actual use according to a normal distribution with mean of 0.37 and standard deviation of 0.04. What proportion of adhesions measured in use are higher than 0.40?

Thanks for the help!

2. Have you tried?

$\displaystyle P(X>0.4) = P\left(Z>\frac{0.4-0.37}{0.04}\right)=\dots$