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Example 4

Several years​ ago, the reported mean age of an inmate on death row was 42.4 years. A sociologist wondered whether the mean age of a​ death-row inmate has changed since then. He randomly selects 35 ​death-row inmates and finds that their mean age is 40.6​, with a standard deviation of 9.9. Construct a 90​% confidence interval about the mean age of death row inmates. What does the interval​ imply? What is the correct hypothesis?