Question

Out of 600 people sampled, 228 preferred Candidate A. Based on this, estimate what proportion of the voting population ( π π ) prefers Candidate A. Use a 90% confidence level, and give your answers as decimals, to three places. < π π

Answer 1

Solution :

Given that,

Point estimate = sample proportion = = x / n = 228 / 600 = 0.380

1 - = 1 - 0.380 = 0.62

Z_/2 = 1.645

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

= 1.645 * (((0.380 * 0.62) / 600)

Margin of error = E = 0.033

A 90% confidence interval for population proportion p is ,

- E < < + E

0.380 - 0.033 < < 0.380 + 0.033

0.347 < < 0.413