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 percent in a 95 percent confidence interval?
A)18
B)307
C)1680
D)2000
E)2965

Question

Quizplus · Accepted Answer

To estimate the sample size, we need to use the formula:

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

Where:
Z = 1.96 (for a 95% confidence interval)
p = proportion of interest (unknown)
q = 1 - p
E = margin of error (0.02)

From the given information, we know that:

n - 2,938 = 13,000
n = 16,938

Substituting these values in the formula:

16,938 = (1.96^2 * p * (1 - p)) / 0.02^2

Solving for p, we get:

p = 0.5

Substituting p in the formula, we get:

n = (1.96^2 * 0.5 * 0.5) / 0.02^2

n ≈ 1,680

Therefore, the best choice is C, with a sample size of 1,680.

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