The effect of the time of day a psychology class is taught on test scores is being studied in an experiment. The difficulty of test questions has been identified as an extraneous factor that could also affect test scores. How can the difficulty of test questions best be addressed to minimize its effect in the experiment? A. Direct control by requiring every class to take the same test B. Blocking into groups based on the teacher of the class C. Replication of the experiment at different times of the year D. Randomization of students in morning and afternoon classes P. S if anyone knows prob and stats I need help really bad

According to the normal model, what percent of receivers would you expect to gain fewer yards than 2 standard deviations below the mean number of yards

What is the nth term rule of the linear sequence below? 27 , 25 , 23 , 21 , 19 , . .

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?