The Random Variable X is normally distributed with mean 560 and standard deviation 20.

Find P(X<530) which I calculated as 0.0668.

However...

It is known that p(|X-560|<a)
Find the value of a

1 answer

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.