Question

5. A person’s blood glucose level and diabetes are closely. X is a random variable that measures the milligrams of glucose per deciliter of blood. After a 12 hour fast, x has an approximate normal distribution with a mean of 85 and a standard deviation of 25. What is the probability in a. through d) that :
a. X is more than 60?
b. X is less than 110?
c. X is between 60 and 110
d. X is greater than 140 (borderline diabetes starts at 140)?
e. What would the minimum X value for blood glucose be if someone ranked in the highest 25% for blood glucose level?

Answer 1

a - d. 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.

e. Reverse process, starting with .25 and its Z score