In 1995,13,000 WWW users were surveyed and asked about their willingness to pay fees for access to websites.Of these,2,938 were definitely not willing to pay such fees.How large a sample is necessary to estimate the proportion of interest to within 2% in a 95% confidence interval?
A)18
B)307
C)1717
D)2000
E)2965

Question

Quizplus · Accepted Answer

The sample size required can be determined using the formula:

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

Where:

Z = the Z-score corresponding to the desired level of confidence (1.96 for 95% confidence)

p = the estimated proportion of interest (unknown)

q = 1 - p

E = the desired margin of error (0.02)

We can estimate p by subtracting the proportion not willing to pay (2,938/13,000 = 0.225) from 1:

p = 1 - 0.225 = 0.775

Substituting these values into the formula:

n = (1.96^2 * 0.775 * 0.225) / 0.02^2 = 1716.79

Rounding up to the nearest integer, we get a sample size of 1717.

In 1995,13,000 WWW Users Were Surveyed and Asked About Their