Chapter PIII, Problem 39RE

(a)

To determine

To find: the reason why researchers conclude that it was appropriate for some of the patients to perform placebo surgery.

Explanation of Solution

The researcher claims that it was important for some of patients to undergo placebo surgery because if there was no placebo surgery, the subjects would realise that they did not receive the surgery and may respond differently so that all volunteers should be informed of the possibility of randomly giving the placebo group assigned.

(b)

To determine

To explain: the explanation for which the experiment 's result is not invalidated.

Explanation of Solution

As patients had to agree to participate in this experiment, a kind of voluntary response group was basically self-selected for the subjects. The results of the experiment are not invalidated because tests often use volunteers and evaluate reactions to a treatment that does not try to establish unknown population parameters. The function of randomization is that the treatment group does not have any knowledge about the random allocation. When sampling, voluntary response is a challenge, but it is not a matter of experimentation.

(c)

To determine

To find: the meaning of the statistically significant.

Explanation of Solution

In this case, the statistically significant indicates that there were discrepancies in the amount of pain relief received by the arthroscopic knee and placebo surgery, but these are minor enough that even if surgery is not a factor, they can be clarified by normal sampling variation.