• the mean of a random sample is 15 and
• the margin of error figured for the 90% confidence interval is 2.5.

1. (3 point) What does the margin of error, "2.5" imply?
2. (3 points) Using information above, figure out lower bound and upper bound of 90% confidence interval to estimate population mean.

(Note that the margin of error is already given as 2.5.)

1. (2 points) Interpret your 90% confidence interval for population mean.
2. (extra credit 2 points) Here is a little challenging part: if you try 95% confidence interval with all other things being constant, what would happen to margin of error? The margin of error 2.5 is given for 90% confidence interval above. Then, now, for 95% confidence interval, margin of error would become less than 2.5 or greater than 2.5?