Easy for some....not for me!

[nursejo98]

The World Health Organization criterion for osteoporosis is a BMD 2.5 standard deviations below the mean for young adults. BMD measurements in a population of people similar in age and sex roughly follow a Normal distribution.

(a) What % of healthy young adults have osteoporosis by the WHO criterion?

(b) Women aged 70 to 79 are of course not young adults. The mean BMD in this age is about -2 on the standard scale for young adults. Suppose that the standard deviation is the same for young adults. What % of this older population have osteoporosis?


I believe that the standard deviation would be 1 and the mean would be 0, but I do not know if there is an actual formula I would use?

Any help you could give is appreciated!
Jolene

[Zanetti]

for (a), this is the formula you should use: P(X< mean - 2.5 sd) = P(N(0,1) < -2.5) = 0.006