1. ANATOMY OF A COMPLETELY RANDOMIZED DESIGN
A Completely Randomized Design is one in which the experimental units are assigned to the treatments entirely at random.
Random assignment
Example 1: As an example, let us consider a travel agency that wishes to compare the effectiveness of three television commercials, advertising vacations in Bora Bora. Thirty people were randomly selected to view the three commercials, and their overall response was assessed. A diagram of the experiment is shown to the right.
Collect data
Group 1
Commercial 1
30 people are
randomly
assigned to
three groups of
10 people.
Assess Responses, Report Conclusions
Commercial 2
Group 2
Group 3
Commercial 3
Random assignment
Collect data
Example 2: Golf ball brands and driving distance: Which brand of golf ball goes the furthest? A group of 50 randomly selected golfers are randomly assigned to test five brands of golf balls