To do these exercises, go to www.macmillanhighered.com/fapp10e.

Question 7.103

2. You can use the Simple Random Sample applet to choose treatment groups at random for a randomized comparative experiment. In outlining the design of the experiment in Exercise 35 (page 333) to compare the growth of cataracts in rats who were given tea extract to rats who were given a placebo, you should randomly choose the subjects (rats) for the first treatment (tea extract).

  1. Use the applet to choose an SRS of 7 out of 14 to receive the first treatment. Which subjects make up this group?
  2. The applet allows you to assign subjects randomly to more than two groups. Suppose you had a total of 36 rats and you wanted to assign a different treatment to each of four 9-rat groups. After you choose the first group, the “Population Hopper” contains the 27 subjects that were not chosen, in scrambled order. Click “Sample” again to choose 9 of these remaining subjects to receive the second treatment. Do this once more to choose the third group. The 9 subjects that remain in the “Population Hopper” form the fourth group. Which of the 36 subjects will receive each of the four treatments?