Health status, part 2.

In Exercise 30, we found a 95%

confidence interval to estimate the average value of air pollution.

a) Suppose the standard deviation of the values was 10 micrograms per cubic meter instead of the 4.83 micrograms per cubic meter used for that interval. What would the larger standard deviation do to the width of the confidence interval (assuming the same level of confidence)?

b) Your classmate suggests that the margin of error in the interval could be reduced if the confidence level were changed to 90% instead of 95%. Do you agree with this statement? Why or why not?

c) Instead of changing the level of confidence, would it be more statistically appropriate to draw a bigger sample?