Question

All deal with a random variable X that follows a normal probability distribution with mean equal to 37 and a standard deviation of 5.

Compute P(X < 39)

Compute P(X < 29 or X > 41)

Compute P(X > 30)

Find the 42nd percentile for this distribution.

Answer 1

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions/probabilities related to the Z scores.

<I>Either-or</I> probabilities are found by adding the individual probabilities.

For last Q, Start with table (.42) and insert Z score into above equation.

Answer 2

PsyDAG, right on thanks