Asked Oct 29, 2019

A small pilot study was conducted to compare cholesterol levels in individuals before and after a low-carbohydrate diet for 6 months. The original study found an insignificant decrease in cholesterol levels but only included six individuals. If the original study found a standard deviation of the difference of 11.8:

A. How many individuals would need to be included to detect a margin of error of 2.5 units.

B. How many would be needed to account for 25% attrition. 


Expert Answer

Step 1

Preliminary calculation:

Using the EXCEL formula “=NORM.S.INV(1– (0.05/2))”, the z-value for 95% confidence level is obtained as 1.96.

Margin of error, E=2.5

Standard deviation of the difference, σd=11.8.

Step 2


Computation of number of individuals would need to be included to detect a margin of error of 2.5 units:

The number of individuals would need to b...


Image Transcriptionclose

п E 2 1.96x11.8 2.5 85.58 86


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