# Random Selection

A study of the ages of motorcyclists killed in crashes involves the random selection of 150 drivers with a mean of 37.1 years. Assuming a standard deviation of 12.0 years, construct a 99% confidence interval estimate of the mean age of all motorcyclists killed in crashes?

A university surveys 36 randomly selected students and asks the number of dollars spent on textbooks/supplies during the academic year. The results (in dollars) are shown below:
425 78 53 699 663 282
845 373 161 22 853 653
366 806 920 562 828 931
641 134 916 38 379 90
388 894 654 639 916 284
700 684 600 425 717 822
Use Excel to construct a 90% confidence interval for the mean dollars spent.
Would a given mean value of \$600 be likely, given the calculated confidence interval?

Question

A teacher figures that final grades in the chemistry department are distributed as: A,   25%; B, 25%; C, 40%; D, 5%; F, 5% At the end of a randomly selected semester, the following number of grades were recorded. Find the critical value x 2/0 to determine if the grade distribution for the department is different than expected.

Use α = 0.01

Grade A B C D F

Number 42 36 60 14 8

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