An estimate is needed of the mean acreage of farms in Ontario, Canada. A 95% confidence interval should have a margin of error of 25 acres. A study 10 years ago in this province had a sample standard deviation of 200 acres for farm size.
a. About how large a sample of farms is needed?
b. A sample is selected of the size found in part a. However, the sample has a standard deviation of 300 acres, rather than 200. What is the margin of error for a 95% confidence interval for the mean acreage of farms?