Which Type of Chi-Squared Procedure Will You Use? Why?
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CHS Statistics Chapter 26 Practice Chi Squared Inference Tests
Answer the following questions and show all your work. Italicized questions should be used to prompt your “thinking” as you complete the procedure.
1. Medical researchers enlisted 90 subjects for an experiment comparing treatments for depression. The subjects were randomly divided into three groups and given pills to take for a period of three months. Unknown to them, one group received a placebo, the second group the “natural” remedy St. John’s Wort, and the third group the prescription drug Posrex. After six months, psychologists and physicians (who did not know which treatment each person had received) evaluated the subjects to see if their depression had returned. Is there evidence that the rate of recurrence differs for some treatments.
Which type of chi-squared procedure will you use? Why?
Set up your hypotheses:
Find the expected counts:
Check conditions:
Calculate the test statistic:
Find the P-value:
State your conclusion:
2. Here are some sample data of color and handedness among AP Statistics students. Is there an association between handedness and eye color? Which type of chi-squared procedure will you use? Why?
Set up your hypotheses:
Find the expected counts: Note that expected cell counts for lefties with green eyes and “other” are too small (3.83 and 2.67) to allow use of a procedure. We overcome this obstacle by combining “green” and “other” into one row – “Other”
Check conditions:
Calculate the test statistic:
Find the P-value:
State your conclusion: