Question

A random sample of 12 men age 60-65 has a mean blood pressure of 142. 3 mmHg and a standard deviation of 20.8 mmHg. Construct a 99% confidence interval for the standard deviation of all men age 60-65.

Answer 1

The 99% confidence interval = (126.93,157.67)

Explanation:

The formula for Confidence Interval =

Mean ± z × Standard deviation /√n

Mean = 142. 3 mmHg

Standard deviation = 20.8 mmHg.

n = 12

Z score for 99% confidence interval = 2.56

Confidence Interval =

142.3 ± 2.56 × 20.8/√12

142.3 ± 2.56 × 6.0044427996

142.3 ± 15.371373567

Confidence Interval

= 142.3 - 15.371373567

= 126.92862643

≈ 126.93

142.3 + 15.371373567

= 157.67137357

≈ 157.67

Therefore, the 99% confidence interval = (126.93,157.67)