In order to determine the proportion of people who favor imposing sales tax for all Internet purchases, the minimum sample size needed for a precision level of 5 percent and a confidence level of 95 percent, is:
A)666.
B)272.
C)384.
D)196.
E)100.

Question

Quizplus · Accepted Answer

To calculate the sample size needed, we can use the following formula:

n = (Z^2 * p * q) / d^2

Where: 
Z = the Z-score for a 95% confidence level, which is 1.96 
p = the estimated proportion of people who favor imposing sales tax for all Internet purchases (we don't know this, so we can use 0.5 for a conservative estimate) 
q = 1 - p 
d = the desired precision level, which is 0.05

Plugging in the values:

n = (1.96^2 * 0.5 * 0.5) / 0.05^2 
n = 384.16

Rounding up to the nearest whole number, we get a sample size of 384. Therefore, the best choice is C.

In Order to Determine the Proportion of People Who Favor