A random sample of 25 observations was selected from a normally distributed population. The average in the sample was 84.6 with a variance of 400
a. Construct a 90% confidence interval for ?.
b. Construct a 99% confidence interval for ?.
c. Discuss why the 90% and 99% confidence intervals are different.
d. What would you expect to happen to the confidence interval in part (a) if the sample size was increased? Be sure to explain your answer.
a. 77.756 to 91.444
b. 73.412 to 95.788
c. As the level of confidence increases, the confidence interval gets wider.
d. Decrease in width since the margin of error decreased.
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