Question

How many business students must be randomly selected to estimate the percentage of using a laptop? We want 91% confidence that the same percentage is within three percentage points of the population percentage?

Answer 1

Given that, margin of error (E) = 0.03 (3%)

confidence level = 0.91

=> significance level = 1 - 0.91 = 0.09

Using standard normal z-table we get, z-score corresponding probability of 0.955 is, Zc = 1.695

We want to find, the sample size, if we don't have a prior estimate for the population proportion,

=> n ≈ 798 (rounded to nearest whole number).

Therefore, required sample size is 798

Note : if you want sample size is to next whole number then, n = 799