Question

Find the sample? size, n, needed to estimate the percentage of adults who have consulted fortune tellers. Use a 0.02 margin of? error, use a confidence level of 90?%, and use results from a prior poll suggesting that 18?% of adults have consulted fortune tellers.

Answer 1

Solution:

Given that,

= 0.18

1 - = 1 - 0.18 = 0.82

margin of error = E = 0.02

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1 / 2 = 0.05

Z_/2 = Z_0.05 = 1.645

Sample size = n = ((Z _{/ 2}) / E)² * * (1 - )

= (1.645 / 0.02)² * 0.18 * 0.82

= 998.5232

= 999

n = sample size = 999