Stats Help?

Question

For women aged 18-24, systolic bp (in mmHg) are normally distributed with a mean of 114.8 and a standard deviation of 13.1. Hypertension is commonly defined as systolic blood pressure above 140.

What is the score that separates the lowest 10% systolic blood pressure from the top 90%?

Answer 1

Using the table at

http://www.itl.nist.gov/div898/handbook/eda/section3/eda3671.htm

you can find that 40% of the population lies 1.28 standard deviations to one side of the mean and by definition 50% of the population is on the other side of the mean.

That makes the answer

114.8 - (13.1 x 1.28) = 98