Question

6. You have been hired by Ford Motor Company to do market research and you must estimate the percentage of households in which a vehicle is owned. How many households must you survey if you want to be 94% confident that your sample percentage has a margin of error within 0.03?

Answer 1

Solution :

Given that,

= 0.5 (assume 0.5)

1 - = 1 - 0.5 = 0.5

margin of error = E = 0.03

At 94% confidence level the z is ,

= 1 - 94% = 1 - 0.94 = 0.06

/ 2 = 0.06 / 2 = 0.03

Z/2 = Z0.03 = 1.88 ( Using z table )

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

= (1.88/ 0.03)2 * 0.5 * 0.5

= 981.777

Sample size =982