In: Statistics and Probability
We have the following sample observations: 9.8, 9.43, 8.97, 9.33, 9.14, 9.55
a). Derive a 90% CI for the population variance. First come up with a pivotal expression, then use that pivotal along with the sample data to generate the confidence interval.
b). Derive a 95% CI for the population mean. First come up with a pivotal expression, then use that pivotal along with the sample data to generate the confidence interval.
From the given data,
= 9.37 , S = 0.2951 , S2 = 0.08708
a)
90% confidence interval for is
(n-1) S2 / /2 < < (n-1) S2 / 1-/2
(6-1) * 0.08708 / 11.070 < < ( 6 - 1) * 0.08708 / 1.145
0.0393 < < 0.3803
90% CI is ( 0.0393 , 0.3803)
b)
95% confidence interval for is
- t * S / sqrt(n) < < + t * S / sqrt(n)
9.37 - 2.571 * 0.2951 / sqrt(6) < < 9.37 + 2.571 * 0.2951 / sqrt(6)
9.0603 < < 9.6797
95% CI is ( 9.0603 , 9.6797)