THREE CLASSES TOOK THE SAME PSYCHOLOGY TEST. THE CLASSWHAT IS THE A...

5. Three classes took the same psychology test. The classwhat is the average of x, y, and z ?sizes and (arithmetic) mean scores are shown.(A) (B) (C) (D) (E) 813 10 1212 15 171 2The overall (arithmetic) mean 85score for the 3 classes+ =x y, or x + y = 40. ThusSince the average of x and y is 20, 2 20 The overall mean score could be found by weighting each meanx + y + z = x + y + 5 = 40 + 5 = 45, and thereforescore by class size and dividing the result by 100, the total of+ + = =x y z45 The best answer is (D).all the class sizes, as follows.33 15.+ (30)(81) + (20)(85)( )( )=85 850 89 .