From the survey in Exercise 11,
a) How would the confidence interval change if the confidence level had been 90% instead of 95%?
b) How would the confidence interval change if the sample size had been 300 instead of 200? (Assume the same sample proportion.)
c) How would the confidence interval change if the confidence level had been 99% instead of 95%?
d) How large would the sample size have to be to make the margin of error half as big in the 95% confidence interval?