Chapter 4.2, Problem 67E

(a)

To determine

To explain how this experiment used comparison.

Explanation of Solution

In this study, researchers want to study about the blood building drugs that can help or not in the brain development of the premature babies.

Researchers randomly assign the babies to the experiment and some of the babies were given the medicines and the others were given no treatments. Therefore, the given experiment used comparison in the sense of checking the effect of two injections and no injection on measures of intelligence, language, and memory. Thus, these were the comparison the researchers want to measure for the development of the babies.

(b)

To determine

To explain the purpose of randomly assigning the babies to the three treatments.

Explanation of Solution

In this study, researchers want to study about the blood building drugs that can help or not in the brain development of the premature babies.

Researchers randomly assign the babies to the experiment and some of the babies were given the medicines and the others were given no treatments. And the purpose of randomly assigning the babies is to make sure that babies who have better or worse intelligence, language, and memory to some extent does not get a favour so that the results of the research could not be biased. And the results can be accurate.

(c)

To determine

To name two variables that were controlled in this experiment and why it was beneficial to control these variables.

Answer to Problem 67E

Two variables are: babies age those who born more than a month premature and their weight.

Explanation of Solution

In this study, researchers want to study about the blood building drugs that can help or not in the brain development of the premature babies.

Researchers randomly assign the babies to the experiment and some of the babies were given the medicines and the others were given no treatments. Therefore, the two variables that are controlled are babies age those who born more than a month premature and their weight. It was beneficial to do the same because less than a month premature is common but the weight of babies less than three pounds is not so common.

(d)

To determine

To explain how this experiment used replication and what is the purpose of replication in this context.

Explanation of Solution

In this study, researchers want to study about the blood building drugs that can help or not in the brain development of the premature babies.

Researchers randomly assign the babies to the experiment and some of the babies were given the medicines and the others were given no treatments. In this experiment the replication is used. The experiment used replication by repeating the injections that were given to the premature babies and the purpose of replication was that to check the effect of injections as time passes.So that the accurate and unbiased results can be figured out.