Question

A social worker is concerned about the number of prescriptions her elderly patients have. She would like to create a 99% confidence interval with a maximum error of 2 prescriptions. Assuming a standard deviation of 5.2, what is the minimum number of patients she must sample?

Answer 1

Solution :

Given that,

standard deviation =   =5.2

Margin of error = E = 2

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.58

sample size = n = [Z/2* / E] 2

n = ( 2.58*5.2 / 2 )2

n =44.997

n=45 (rounded)