Question

A researcher is interested in the decrease in mean bone fractures in postmenopausal women treated with vitamin and calcium supplementation. Assuming that the population under investigation has a standard deviation of 3 bone fractures, and that the goal margin of error of the estimate is plus or minus 0.4 fractures. How many women should be sampled to attain an estimate with 95% confidence

Answer 1

Answer: 217 women should be sampled to attain an estimate with 95% confidence.

Explanation:

Let s be the prior population standard deviation.

Formula to find the sample size:
`n=((z^** s)/(E))^2`, E=Margin of error

Given: s= 3

E= 0.4

Critical zvalue for 95% = 1.96

So,
`n=((1.96*3)/(0.4))^2`

`=216.09\approx217`

Hence, 217 women should be sampled to attain an estimate with 95% confidence.