150 sixth-form students are sampled (a simple random sample)from 3000 in sixth-form colleges across the West Midlands.From the sampled students,an average IQ of 115 is determined,with a standard deviation of 10.What is the 99% confidence interval?
A)115 ± 0.01
B)115 ± 1.22
C)115 ± 2.10
D)115 ± 3.22

Question

Quizplus · Accepted Answer

The 99% confidence interval is 115 ± 2.10. This is because the standard error of the mean is 10/√150 = 0.632, and the 99% confidence level corresponds to a z-score of 2.576. Therefore, the confidence interval is 115 ± 2.576 * 0.632 = 115 ± 2.10.

150 Sixth-Form Students Are Sampled (A Simple Random Sample)from 3000