9. The sodium content of twenty 300-gram boxes of organic cornflakes was determined. The data (in_milligrams) are as follows: 131.15, 130.69, 130.91, 129.54, 129.64, 128.77, 130.72, Saved to this PC 28.24, 129.65, 130.14, 129.29, 128.71, 129.00, 129.39, 130.42, 129.53, 130.12, 129.78, 130.92.
a. Can you support a claim that mean sodium content of this brand of cornflakes differs from 130 milligrams? Use \( \alpha=0.05 \).
b. Explain how the question in part could be answered by constructing a two-sided confidence interval on the mean sodium content.