Unit 3 Experiments

Estelle's cornfield is divided into 6 regions. She wants to know if a new pesticide is as effective as the pesticide that she currently uses. She randomly assigns each of the 6 regions to either the new or current pesticide for a month, and she'll compare the effectiveness of the pesticides.

A completely randomized design

A surgeon developed a new procedure for knee replacement surgery. To study its effectiveness, they recruit patients who need knee replacement surgery and are willing to participate in a blind study. The surgeon randomly assigns each volunteer to receive either the new procedure or the standard procedure. After the surgeon performs the procedure, they monitor each patient to see if one group has better results than the other.

BLIND-The volunteers are unaware of which surgery they receive.

The professor assigns each student a number from 1 to 150 and uses a random number generator to assign the first 75 students selected to use the new study tool. The remaining 75 subjects are assigned to use the previous study tool.

Completely Randomized

They use a random number generator to select 100 customer account numbers to offer the incentive. The remaining 100 customers are assigned to the control group.

Completely Randomized

They assign each subject a number from 1 to 100 and use a random number generator to assign the first 50 subjects selected to take the driving test with one music volume. The remaining 50 subjects are assigned to take the test with the second music volume.

Completely randomized

The company ranks the customers according to total cost of purchases made the previous year. For every 2 customers, in order, from the list, the online retailer randomly assigns one customer to the treatment group and the other to the control group.

Matched Pairs

The company ranks the customers according to total health care costs for the previous year. For every 2 customers, in order, from the list, the insurance company randomly assigns one customer to be offered the incentive and the other to the control group.

Matched Pairs

The professor ranks the students according to cumulative average in the prerequisite course. For every 2 students, in order, from the list, the professor flips a coin to assign one student to use the new study tool and the other to use the previous study tool.

Matched Pairs

Half of the 50 males are randomly assigned to the treatment group, and the other half are assigned to the control group. The same method is used to randomly assign half of the 50 females to the treatment group and the other half to the control group.

Randomized Block

Half of the freshmen are randomly assigned to use the new study tool, and the other half are assigned to use the previous study tool. The same method is used to randomly assign half of the sophomores, half of the juniors, and half of the seniors to each study tool.

Randomized Block

Half of the males are randomly assigned to the treatment group, and the other half are assigned to the control group. The same method is used to randomly assign half of the females to the treatment group and the other half to the control group.

Randomized Block

can establish a casual relationship or conclusion

Randomized prospective studies/ experiments

A professor wants to study the effectiveness of a new study tool for a course. There are 150 students registered for the course. The professor assigns each student a number from 1 to 150 and uses a random number generator to assign the first 75 students selected to use the new study tool. The remaining 75 subjects are assigned to use the previous study tool.

Completely randomized

Researchers working on a vaccine for HIV recruited over 16,000 volunteers for an experiment. Each volunteer was randomly assigned to receive monthly injections of either the vaccine or a placebo for a year. The researchers were curious if subjects who received the vaccine would be less likely to contract HIV than subjects who received the placebo.

DOUBLE BLIND -Both the subjects and the researchers are unaware of who is receiving the vaccine and who is receiving the placebo.