Serum cholesterol is an important risk factor for coronary disease. Suppose that serum cholesterol is approximately normally distributed with mean 227.3 mg/dL and standard deviation 47.6 mg/dL.

1. Cholesterol levels in the top 15% are classified as high enough to warrant risk for heart disease. What cholesterol level corresponds to this cut-off?

• z =
• cholesterol =mg/dL

1. Suppose cholesterol levels in the bottom 28% are classified as normal. What cholesterol level corresponds to a normal reading?

• z =
• cholesterol =mg/dL

1. Between what two values do the middle 36% of cholesterol readings fall?

• z =+
• betweenmg/dL andmg/dL

Note: z-scores should include 2 decimal places; all other answers should be rounded to 3 decimal places.