Question

A random sample of 28 items is drawn from a population whose standard deviation is unknown. The sample mean is x = 790 and the sample standard deviation is s=15. Use Appendix D to find the values of Student'st (a) Construct an interval estimate of u with 99% confidence. (Round your answers to 3 decimal places.) The 99% confidence interval is from 780:36 to 737854 (b) Construct an interval estimate of u with 99% confidence, assuming that s- 30. (Round your answers to 3 decimal places.) The 99% confidence interval is from to al places.) (c) Construct an interval estimate of u with 99% confidence, assuming that s. 60. (Round your answers to 3 decimal places.) The 99% confidence interval is from to (d) Describe how the confidence interval changes as s increases. The interval stays the same as s increases References The interval gets wider as s increases. The interval gets narrower ass increases

Answer 1

a)

sample mean 'x̄=	790.000
sample size   n=	28.00
sample std deviation s=	15.000

for 99% CI; and 27 df, value of t=	2.771
margin of error E=t*std error    =	7.855
lower bound=sample mean-E =	782.145
Upper bound=sample mean+E =	797.855

from above 99% confidence interval for population mean =(782.145 ,797.855)

b)

99% confidence interval for population mean =(774.290 ,805.710)

c)

99% confidence interval for population mean =(758.580 , 821.420)

d)