Chapter 6.2, Problem 6.51E

(a)

To determine

To describe the design of the experiment and also explain how was blocking incorporated and why.

Explanation of Solution

  $\begin{array}{l}\text{We have 11 volunteers and two treatments: caffeine and placebo}\text{.}\\ \text{We randomly assign 6 of the volunteers to group 1 while the remaining volunteers}\\ \text{to group 2}\text{.}\\ \text{Group 1 will receive caffeine and will then receive a placebo}\text{.}\\ \text{Group 2 will receive placebo first and will then receive caffeine}\text{.}\\ \text{We will then compare the results on the tapping tasks}\text{.}\end{array}$

(b)

To determine

To explain why does the researchers randomized the order in which subjects received the two treatments.

Explanation of Solution

The order was randomized because if the volunteers first received the caffeine and noticed the effect then they will expect to get the same result on the second study period. The more the volunteers believe in the effect of the treatment the stronger the placebo effect will be.

We will then randomized the treatments such that we can take into the account the difference in the placebo effect among first receiving the caffeine and first receiving the placebo since we expect the placebo effect to be strong among those that first receive caffeine.

(c)

To determine

To identify could this experiment have been carried out in a double blind manner and explain.

Answer to Problem 6.51E

Yes.

Explanation of Solution

In this case it is possible to make sure that the experiment is double blinded by making sure that the two types of capsules are identical in look and by making sure that the people who hand out the medicine or measure the results are unaware of which treatment is received by which volunteers.