The effect of the time of day a class is taught on test scores is being studied in
an experiment. Student ability has been identified as an extraneous factor that
could also affect test scores.
How can student ability best be addressed to minimize its effect in the
experiment?
O A. Direct control of what textbook is used
O B. Blocking into groups based on the teacher of the class
O C. Randomization of students in morning and afternoon classes
O D. Replication of the experiment at different times of the year

The only way to minimize this effect would be through randomization of students in morning and afternoon classes. Doing so apply the factor of skill from an individual student to either time of day class greatly lessens the overall effect that it has on the results. This therefore, minimizes the effect it has on the experiment itself, since the same students that have been studying in a certain time of day would be randomized and not have the same environment that they are used to.