Question

Select all experiments that use a completely randomized design.

A)A computer scientist is testing new antivirus software on computers that were built in the last month. Ten computers with operating system A were randomly selected, and ten were chosen with operating system B. Five computers with each operating system were randomly assigned to be scanned with the new software, five to the existing software.


B)To test an epidermal treatment on fish in polluted stream water, 50 fish with epidermal abrasions from the same stream are randomly placed into two aquariums. One aquarium receives the epidermal treatment, and the other receives no treatment.


C)In a fertility study designed to test whether a new supplement helps individuals increase egg production, a computer randomly assigns participants into a group receiving the supplement and a group receiving an inactive pill.


D)Scientists assign the plants on the outer edge of a garden to an old fertilizer and plants in the middle of the garden to a new fertilizer. At the end of one month, the scientists randomly select four plants from each group to measure growth and determine the results of the study.


E)Participants in a study to determine the effects of a new hair-growth remedy are divided into groups based on age, and each subject in each group is randomly assigned to receive the new remedy, an existing remedy, or a placebo.

Answer 1

The experiments that use completely randomized designs are:

B)To test an epidermal treatment on fish in polluted stream water, 50 fish with epidermal abrasions from the same stream are randomly placed into two aquariums. One aquarium receives the epidermal treatment, and the other receives no treatment.

C)In a fertility study designed to test whether a new supplement helps individuals increase egg production, a computer randomly assigns participants into a group receiving the supplement and a group receiving an inactive pill.

In a completely randomized design, participants or subjects are randomly assigned to different treatment groups. This ensures that each participant has an equal chance of being assigned to any group.

In experiment B, fish with epidermal abrasions are randomly placed into two aquariums, receiving either the treatment or no treatment. In experiment C, participants are randomly assigned to receive the supplement or an inactive pill. These designs demonstrate a completely randomized approach.

On the other hand, experiments A, D, and E involve some level of non-random assignment or grouping based on certain criteria, making them not completely randomized.

Experiments B and C utilize a completely randomized design, ensuring unbiased group assignment, while experiments A, D, and E lack complete randomness in their design.