Question

Given that x is a normally distributed random variable with a mean of 28 and a standard deviation of 7, find the following probability:

P(x<28)

I understand that the means is 28 and the standard deviation is 7. However what I don't understand is how to get the value of x.

Do I subtract 28 from 7 to get 21 and square it for the answer?

or do I use the formula of z= x-mean/standard deviation? and if so how do I work the formula with out the value of x?

Use Z = (score-mean)/SD

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

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