A group of researchers calculates the mean quantity of sodium (in milligrams) in selected branded cereals consumed by people in each serving. To do so, the group takes a random sample of 30 branded cereals and obtain the quantity (in milligrams) below.

From past studies, the research council assumes that σ is 70.7 milligrams.

Use the information to construct 90% and 99% confidence intervals for the population mean. Interpret the results and compare the widths of the confidence intervals.

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