A machine that packages 18-ounce (510-gram) boxes of sugar-coated wheat cereal is being studied. The weights for a random sample of 100 boxes of cereal packaged by this machine are contained in the data file Sugar.
a. Find a 90% confidence interval for the population mean cereal weight.
b. Without doing the calculations, state whether an 80% confidence interval for the population mean would be wider than, narrower than, or the same as the answer to part a.