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