59. The article Computer-Assisted Instruction Augmented with Planned Teacher/Student Contacts

(J. Experiment. Ed., Winter 1980—1981: 120—126)

compared ve different methods for teaching descriptive statistics. The ve methods were traditional lecture and discussion (L/D), programmed textbook instruction (R), programmed text with lectures

(R/L), computer instruction (C), and computer instruction with lectures (C/L). Forty- ve students were randomly assigned, 9 to each method. After completing the course, the students took a 1-hour exam. In addition, a 10-minute retention test was administered 6 weeks later. Summary quantities are given.

Exam Retention Test Method si si L/D 29.3 4.99 30.20 3.82 R 28.0 5.33 28.80 5.26 R/L 30.2 3.33 26.20 4.66 C 32.4 2.94 31.10 4.91 C/L 34.2 2.74 30.20 3.53 The grand mean for the exam was 30.82, and the grand mean for the retention test was 29.30.

a. Does the data suggest that there is a difference among the ve teaching methods with respect to true mean exam score? Use a  .05.

b. Using a .05 signi cance level, test the null hypothesis of no difference among the true mean retention test scores for the ve different teaching methods.