Determine whether each study is a randomized comparative experiment.

Question

Determine whether each study is a randomized comparative experiment. If it is, describe the treatment, the treatment group, and the control group. If it is not, explain why not and discuss whether the conclusions drawn from the study are valid.

Shot Speed

A company wants to know if their cleats make soccer players shoot the ball with more velocity. The company randomly selects 100 professional soccer players who use their cleats and 100 professional soccer players who use other cleats. They measure the velocity of each player's shot using film from games and conclude that their cleats make players shoot the ball with higher velocity.

A) The study is not a randomized comparative experiment.

B) The study is a randomized comparative experiment.

Study Habits

A school wants to find the effect of study habits on its students' grades. Students taking a statistics course are randomly divided into two groups of equal size. The first group is instructed to study statistics for 2 hours each day while the second group is instructed to not study for statistics (please don't do this). At the end of the year, both groups are given the same final exam and the group which studied 2 hours each day received higher scores on average.

A) The study is not a randomized comparative experiment.

B) The study is a randomized comparative experiment.

For the study that is not a randomized comparative experiment:

The study is not a randomized comparative experiment because (there are no control and treatment group /individuals were not randomly assigned to the control group and the treatment group / the study is not an experiment). The conclusion of the study (is not valid/is valid/may or may not be valid).

For the study that is a randomized comparative experiment:

The treatment is (the use of the company's cleats/the use of other cleats/studying for 2 hours each day/not studying). The treatment group (is the individuals who use the company's cleats/the individuals who use other cleats/the individuals who study for 2 hours each day/the individuals who do not study). The control group (is the individuals who use the company's cleats/the individuals who use other cleats/the individuals who study for 2 hours each day/the individuals who do not study).

Answer 1

Hi Chris,

To get started, we have to understand the definition of a randomized comparative experiment. Randomization refers to the random assignment of subjects into an experimental (or treatment) group and into a control group. Note that the experimental group and the treatment group are the same thing. In a comparative experiment, we compare the results of two or more treatment groups. In other words, we have to have at least two treatment groups in an experiment in order to have a comparative study. We do not need to have a control group in comparative experiment, but we can if we want to.

Now let's look at the two studies in the question:

In the "Shot Speed" study, we have an experimental group, consisting of 100 professional soccer players who wear cleats from this particular company, and we have a control group, which consists of 100 professional soccer players who use cleats from any other company. Here, the treatment is the company's cleats (the cleats are considered to be a treatment since they are said to improve shot speed), so the treatment group is the group of 100 soccer players who use this company's cleats. Because the experimental and control groups were assigned randomly, we have randomization. However, because there is only one experimental group, we do not have a comparative experiment.

Similarly, in the "Study Habits" experiment, we have an experimental group, made up of statistics students who study 2 hours a night, and a control group, consisting of statistics students who were instructed not to study. Again, there is randomization, but this is not a comparative experiment since there is only one treatment group.