Questions: Subjects or experimental units are randomly assigned to the control or treatment groups.

Transcript text: Subjects or experimental units are randomly assigned to the control or treatment groups.

Solution

Solution Steps

Step 1: Identify the key concept of a completely randomized experiment

A completely randomized experiment involves randomly assigning subjects or experimental units to either the control or treatment groups. This ensures that each subject has an equal chance of being assigned to any group, minimizing bias.

Step 2: Analyze the options provided

Option 1: "Receive no treatment and serve as a baseline for comparison."
This describes the control group, not the randomization process.
Option 2: "Looks like the treatment but is inert."
This describes a placebo, not randomization.
Option 3: "Subjects or experimental units are randomly assigned to the control or treatment groups."
This matches the definition of a completely randomized experiment.
Option 4: "Influenced by the experiment."
This is vague and unrelated to randomization.
Option 5: "Receives the treatment."
This describes the treatment group, not randomization.
Option 6: "The researcher determines the effect of the first factor while carefully controlling the effects of potential confounding variables."
This describes controlling for confounders, not randomization.
Option 7: "Subjects or experimental units are divided into pairs, matched on one or more characteristics as possible. Then from each pair, one subject is assigned to the control group and one is assigned to the treatment group."
This describes a matched-pairs design, not a completely randomized experiment.
Option 8: "The researcher simply observes the effect of a risk factor or treatment without trying to control group."
This describes an observational study, not an experiment.
Option 9: "Subjects or experimental units are first divided into groups for blood type and then within each group, subjects are randomly assigned to the control or treatment groups."
This describes a stratified randomized experiment, not a completely randomized experiment.

Step 3: Select the correct option

The correct definition of a completely randomized experiment is provided in Option 3: "Subjects or experimental units are randomly assigned to the control or treatment groups."