Question 813:

Asked on October 2, 2009

Tags: Z-Score , NORMSDIST

1

Answer:

No answer provided yet.

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.