response rate with a probability of 0.90 that the error estimation is less than 0.06?

Question

Suppose one of the executives would like to estimate the response rate for another welcome screen format. How many web users should be selected for the survey if the executive wishes to estimate the response rate with a probability of 0.90 that the error estimation is less than 0.06?

Answer 1

That is the formula for the confidence interval of a proportion.

We can set the right side of the interval (the margin of error) equal to 0.06 and solve for n

the Z_0.05 = 1.645

use 0.5 for p, as that is the most conservative value.

1.645 * sqrt((.5*.5)/n) = 0.06

Solving for n,

n = 13.7

We round up to 14 for the answer. We can't have a fraction of a person