A consultant was called to assist the police department of a large metropoli-

tan city in evaluating its human relations course for new ocers. He planned a two-factor factorial experiment where the treatments were A|the type beat to which ocers were assigned, and B|the length of the human rela-

tions course. A sample of 45 new ocers was chosen, and 5 were randomly assigned to each of the 9 treatment combinations. A test was developed to measure ocers' attitude toward minority groups and was administered to the participating ocers after their training had ended and they had ex-

perienced two weeks on their beat. Better attitudes result in higher scores on this test. Analysis of the data revealed a signicant A×B interaction eect between the type beat and length of human relations course. The table below shows the mean test scores for the 9 combinations of treatment levels.

(a) Construct an interaction graph.

(b) Write an interpretation of the interaction in a few complete sentences.

Transcribed Image Text:

Type Beat 5 Hours Length of Human Relations Course 10 Hours 15 Hours upper-class beat 34.4 35.5 39.2 middle-class beat 30.2 32.4 34.7 inner-city beat 20.1 39.4 54.3