Question 813:

1

What we need to do is find the percent of men and women who have serum levels above 200. To find that, we first need to find the z-score for men and z-score for women. The general formula is (x-mean)/sd where x in this case is 200.

For men we get a z-score of : (200-195)/12 = .41667

For women we get a z-score of : (200-185)/12 = 1.25

Now we need to find the amount of area under the normal curve that is .41667 and 1.25 standard deviations. To do so we can use the excel function =NORMSDIST() and we get the areas of .6615 and .8944. Since we're only interested in those with serum cholesterol above 200, we want the area above each percentage or 1-.6615 and 1-.8944 = .33846 and .10565 for men and women respectively.

To find our answer, we just multiply these percentages times 5000 (since the men and women were equally divided). We get = .338461*5000 = 1692.306 and .10565*5000 = 528.2489. Adding together we get = 2220.554 and rounding up that means 2221 students will be at increased risk out of 10000.