Question

Assume that the proportion of online shopping at Best Buy is 25%. The sample size with 5% margin of error and 95% confidence would be: Select one: a. n = 288. b. n = 289. c. n = 289.15. d. n = 288.12.

Answer 1

Solution :

Given that,

= 0.25

1 - = 1 - 0.25 = 0.75

margin of error = E = 5% = 0.05

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96 ( Using z table ( see the 0.025 value in standard normal (z) table corresponding z value is 1.96 )

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

= (1.96 / 0.05)2 * 0.25 * 0.75

= 289