In Exercises 33–36, identify which of these designs is most appropriate for the given experiment: completely randomized design, randomized block design, or matched pairs design.


Lunesta Lunesta is a drug designed to treat insomnia. In a clinical trial of Lunesta, amounts of sleep each night are measured before and after subjects have been treated with the drug.

Verified step by step guidance

1. Identify the key elements of the experiment: the treatment (Lunesta), the subjects (individuals with insomnia), and the measurements (amounts of sleep each night before and after treatment).
2. Consider the nature of the measurements: since the same subjects are measured before and after the treatment, this suggests a comparison of two related samples.
3. Recognize that the design involves comparing the same subjects under two different conditions (before and after treatment), which is characteristic of a matched pairs design.
4. Understand that a matched pairs design is appropriate here because it controls for individual variability by using each subject as their own control.
5. Conclude that the matched pairs design is most suitable for this experiment as it allows for a direct comparison of the effects of Lunesta on the same individuals, enhancing the reliability of the results.

Key Concepts

Completely Randomized Design

A completely randomized design is an experimental setup where all subjects are randomly assigned to different treatment groups. This design is useful when the subjects are homogeneous, and the goal is to ensure that each treatment group is statistically equivalent, minimizing bias and confounding variables.

Randomized Block Design

A randomized block design involves grouping subjects into blocks based on a certain characteristic before randomly assigning treatments within each block. This design is effective when there are known sources of variability among subjects, allowing for more precise comparisons by controlling for these differences.

Matched Pairs Design

A matched pairs design is used when subjects are paired based on similar characteristics, and each pair is split to receive different treatments. This design is particularly useful in before-and-after studies, like the Lunesta trial, as it controls for individual variability by comparing each subject to themselves, enhancing the reliability of the results.