A random sample of 25 items is drawn from a population whose standard deviation

Question

A random sample of 25 items is drawn from a population whose standard deviation is unknown the sample mean is x = 850 and the sample standard deviation is s = 15 Use Appendix D to find the values of Student's t. Construct an interval estimate of mu with 95% confidence (Round your answers to 3 decimal places.) the 95% confidence Interval is from to Construct art interval estimate of mu with 95% confidence, assuming that s = 30 (Round your answers to 3 decimal places.) the 95% confidence interval Is from

Explanation / Answer

Answers to the question:

n = 25
Xbar = 850
Stdev =s=15
The t value corresponsng to df = n-1=24 and alpha=.05( 2 tailed) is 2.064

a.

CI is xbar+/-t*s/sqrt(n)
850 +/- 2.064*15/sqrt(25)
=843.8 to 856.2

b.

CI is xbar+/-t*s/sqrt(n)
850 +/- 2.064*30/sqrt(25)
=837.616 to 862.384

c.

CI is xbar+/-t*s/sqrt(n)
850 +/- 2.064*60/sqrt(25)
=825.232 to 874.768

d.
As s increases CI increases.
so, b option is right

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