Chapter 12.1, Problem 29E

(a)

To determine

To Explain: the reason that this is the experiment and not an observational study.

Answer to Problem 29E

Experiment

Explanation of Solution

Given:

  

An experiment intentionally puts some treatment on individuals so that their reactions can be followed.

An observational study tries to collect the information without disturbing the view they are viewing.

Experiment

The reason is that each subject has 2 treatments (read words and say colours).

(b)

To determine

To find: the design by the researcher is completely randomized or blocks design and explain about the selection of experimental design.

Answer to Problem 29E

Randomized block design

Explanation of Solution

Given:

  

A randomized block design, the reason is that every subject received two treatments and therefore every subject received two treatments and therefore each subject constructs a block

The other option (a completely randomized design) would require that every subject receive 1 treatment and therefore not 2.

(c)

To determine

To Explain: the reason of the random assignment.

Answer to Problem 29E

Eliminate possible confounding

Explanation of Solution

Given:

  

When their effects on a response variable cannot be distinguished from each other, two variables are assumed

Random assignment is used to make different groups of subjects as similar as possible, to eliminate possible confounding differences in the groups before the experiment may affect the output results).

In this case, the order in which the two treatments are mention is randomly assigned such that experience does not affect the results as there are more familiar with the list after the first treatment and therefore it would be likely to get a better time on the second treatment. Therefore experience could be a possible confounding variable when there is no random assignment occurs.