Question

A survey of 400 women shoppers found that 21% of them shop on impulse. Find the 99% confidence interval for the true proportion of women shoppers who shop on impulse

Answer 1

Solution :

Given that,

Point estimate = sample proportion = = 0.21

Z_/2 = 2.576

Margin of error = E = Z _{/ 2} * (( * (1 - )) / n)

= 2.576* (((0.21 * 0.79) / 400)

= 0.052

A 99% confidence interval for population proportion p is ,

- E < p < + E

0.21 - 0.052 < p < 0.21 + 0.052

0.158 < p < 0.262

(0.158 , 0.262)