Question

Suppose that it is known that an experimental drug lasts in a human body with a population standard deviation of 8 minutes. What sample size is necessary in order to estimate the mean time that the drug lasts in a human body with a 90% level of confidence and 10% margin of error?  Remember to round the appropriate critical value to three decimal places and round the sample size up to the nearest whole number.

Answer 1

Solution :

Given that,

standard deviation =   =8

Margin of error = E = 0.10

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z0.05 = 1.645

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

n = ( 1.645 * 8 / 0.10 )2

n =17318.56

Sample size = n =17319