Exercise 7.41 on page 485 describes an experiment on helping cocaine addicts break the cocaine addiction, in which cocaine addicts were randomized to take desipramine, lithium, or a placebo. The results (relapse or no relapse after six weeks) are summarized in Table 7.35.

Table 7.35

(a) In Exercise 7.41, we calculate a χ² statistic of 10.5 and use a χ² distribution to calculate a p-value of 0.005 using these data, but we also could have used a randomization distribution. How would you use cards to generate a randomization sample? What would you write on the cards, how many cards would there be of each type, and what would you do with the cards?
(b) If you generated 1000 randomization samples according to your procedure from part (a) and calculated the χ² statistic for each, approximately how many of these statistics do you expect would be greater than or equal to the χ² statistic of 10.5 found using the original sample?

Exercise 7.41

Cocaine addiction is very hard to break. Even among addicts trying hard to break the addiction, relapse is common. (A relapse is when a person trying to break out of the addiction fails and uses cocaine again.) Data 4.7 on page 267 introduces a study investigating the effectiveness of two drugs, desipramine and lithium, in the treatment of cocaine addiction. The subjects in the six-week study were cocaine addicts seeking treatment. The 72 subjects were randomly assigned to one of three groups (desipramine, lithium, or a placebo, with 24 subjects in each group) and the study was double-blind. In Example 4.29 we test lithium vs placebo, and in Exercise 4.140 we test desipramine vs placebo. Now we are able to consider all three groups together and test whether relapse rate differs by drug. Ten of the subjects taking desipramine relapsed, 18 of those taking lithium relapsed, and 20 of those taking the placebo relapsed.

Transcribed Image Text:

No relapse Total Relapse Desipramine Lithium 24 24 10 14 6. 4 18 Placebo 20 48 24 Total 72 24