Question

If n=450 and p' (p-prime) = 0.9, construct a 90% confidence interval.

Give your answers to three decimals.

Answer 1

Solution :

Given that,

Point estimate = sample proportion = = 0.9

1 - = 1 - 0.9 = 0.1

Z/2 = 1.645

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

= 1.645 * (((0.9 * 0.1) / 450)

Margin of error = E = 0.023

A 90% confidence interval for population proportion p is ,

- E < p < + E

0.9 - 0.023 < p < 0.9 + 0.023

0.877 < p < 0.923

The 90% confidence interval for the population proportion p is : 0.877 , 0.923