A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers placed an ad onl
ine asking volunteers to participate in the study, and 100 subjects replied. They are informed that one group will receive a new cream and the other group will receive a cream with no active ingredient. The researchers believe that sun exposure may affect the cream’s effectiveness. The subjects are then asked about their outdoor activity, and 42 of the subjects state they spend more than 50% of their day outside. The 42 subjects are randomly assigned to the two treatments. The remaining 58 subjects are also randomly assigned to the two treatments. All subjects are exposed to poison ivy and given their cream. They are asked to return in three days and report their level of irritation. Is this a randomized block design?
A.) Yes, the subjects could be randomly assigned to two different treatments.
B.) Yes, the participants are grouped by sun exposure, and then both treatments are randomly assigned within each group.
C.) No, the groups have an equal number of subjects.
D.) No, the subjects were not paired by age to determine if it affected the cream’s effectiveness.
B: Yes, the participants are grouped by sun exposure, and then both treatments are randomly assigned within each group.
Step-by-step explanation:
Randomized block design is one in which the experimental units are categorized into groups which we call blocks. Thereafter, treatments will be randomly allocated to the experimental units inside each of the blocks.
Now, from the question, we can see that they were grouped in Blocks according to their outdoor activity which is degree of exposure to the sun. Thereafter the individual groups are randomly assigned treatments.
