Question

62% of Americans like a certain car brand

Margin of error is 5.5%

Confidence Level is 95%

a) Find the number of people surveyed

Choose

a) 77 b) 100 c) 300 d)600 e)1200

b)What is the 90% confidence interval for the population proportion who like the car brand.

a) (5%, 95%) b) (10%, 90%) c) (56.5%, 67.5%) d) (57.4%, 66.6%) e) (53%, 71%)

Answer 1

a. Here z value for 95% CI is 1.96 as P(-1.96<z<1.96)=0.95

Margin of Error is E=0.055 and p=0.62

So we will find n using formula of E,

So

Hence answer is c) 300

b. z value for 90% CI is 1.645 as P(-1.645<z<1.645)=0.90

So Margin of Error is

Hence CI is

Hence answer here is d) (57.4%, 66.6%)