1. under what conditions would you decide to use a t-test instead of a z test?
2. if you are comparing one sample mean against a population mean and your mean is based
upon 20 subjects, how many degrees of freedom would you have?
3. a new kind of glasses was developed to major-league baseball players. the baltimore
orioles obtained the patent rights to these glasses and used them during the 2015 season. buck
showalter (the manager of the orioles) believes the glasses influenced the batting average of his
players. in order to test this he computed the batting average of his 21 players and compared it to
the average for the entire league. the batting average for the orioles was.287, and s-.020. the
batting average for the entire league was u .269.
a. state your null and alternative hypothesis.
b. conduct the appropriate statistic.
c. state your conclusion.
4. a marriage counselor believes she has a therapy for married couples which will change their
levels of "marital bliss." in the general population it has been determined that couples score an
average of 65 out of 100 on the marital bliss survey. the counselor picks 12 couples at random
and after therapy their scores were as follows:
75, 70, 85, 60, 57, 69, 75, 89, 92, 90, 79, 100
a. can she claim that her therapy changes "marital bliss? "
(be sure to provide a null and alternative hypothesis and compute the appropriate statistic to
support your conclusion)