Chapter 8 Study Problems
1. Distinguish between directional and nondirectional tests.
2. A group of 200 students took the Kaplan course in hopes that it would improve
their SAT scores on the math section. The students had an average of 520 after the
course, compared to the national mean of 500 (the population standard deviation is
100). Use an alpha level of .05 to test the nondirectional hypothesis that those
who took the Kaplan course di
!
ered in math score from the national average. Write
out and label all steps of hypothesis testing.
3. A small business wants to examine whether its clients are paying their invoices
within 30 days, as is the policy. They obtain the number of days before payments
were received on 8 randomly chosen accounts. These were: 24, 25, 31, 31, 33,
34, 36, 42. Using alpha of .05, test the nondirectional hypothesis that the days
before payment was received di
!
ers from 30. (Note that the critical value was
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 Spring '10
 DAMARE
 Statistics, Null hypothesis, #, Statistical hypothesis testing, rejection region

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