Use the given degree of confidence and sample data to construct a confidence interval for the population mean 39 packages are randomly selected from packages received by a parcel service The sample has a mean weight of 21 1 pounds and a standard deviation of 3 7 pounds What is the 95 percent confidence interval for the true mean weight of all packages received by the parcel service O 19 6 22 6 O 20 1 22 1 O 19 7 22 5