6.19 Mean TRAP in young women. For many important processes that occur in the bo
ID: 3338720 • Letter: 6
Question
6.19 Mean TRAP in young women.
For many important processes that occur in the body, direct measurement of characteristics of the process is not possible. In many cases, however, we can measure a biomarker, a biochemical substance that is relatively easy to measure and is associated with the process of interest. Bone turnover is the net effect of two processes: the breaking down of old bone, called resorption, and the building of new bone, called formation. One biochemical measure of bone resorption is tartrate-resistant acid phosphatase (TRAP), which can be measured in blood. In a study of bone turnover in young women, serum TRAP was measured in 31 subjects. The mean was 13.2 units per liter (U/l). Assume that the standard deviation is known to be 6.5 U/l. Give the margin of error and find a 95% confidence interval for the mean TRAP amount in young women represented by this sample.
6.33 Required sample size for specified margin of error.
6.34 Adjusting required sample size for dropouts.
Refer to the previous exercise. In similar previous studies, about 20% of the subjects drop out before the study is completed. Adjust your sample size requirement so that you will have enough subjects at the end of the study to meet the margin of error criterion.
Please help with question 6.33 and 6.34! Thanks!
OExplanation / Answer
Q33.
Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.05% LOS is = 1.96 ( From Standard Normal Table )
Standard Deviation ( S.D) = 6.5
ME =1.5
n = ( 1.96*6.5/1.5) ^2
= (12.74/1.5 ) ^2
= 72.137 ~ 73
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