Many school districts are attempting to both reduce costs and motivate students by using...

Many school districts are attempting to both reduce costs and motivate students by using computers as instructional aides. A study was designed to evaluate the use of computers in the classroom. A group of students enrolled in an alternative school were randomly assigned to one of four methods for teaching adding and multiplying fractions. The four methods were lectures only (L), lectures with remedial textbook assistance (L /R), lectures with computer assistance (L/C), and computer instruction only (C). After a 15-week instructional period, an exam was given. The students had taken an exam at the beginning of the 15-week period and the difference in the scores of the two exams is given in the following table. The school administrator wants to determine which method yields the largest increase in test scores and provides the most consistent gains in scores.

Which method of instruction appears to be the most successful? Provide all relevant tests, confidence intervals, and plots to justify your conclusion.