How much assistance should accounting professors provide students for completing homework? Is too much assistance counterproductive? These were some of the questions of interest in a Journal of Accounting Education (Vol. 25, 2007) article. A total of 75 junior-level accounting majors who were enrolled in Intermediate Financial Accounting participated in an experiment. All students took a pretest on a topic not covered in class; then each was given a homework problem to solve on the same topic. However, the students were randomly assigned different levels of assistance on the homework. Some (20 students) were given the completed solution, some (25 students) were given check figures at various steps of the solution, and the rest (30 students) were given no help. After finishing the homework, each student was given a posttest on the subject. One of the variables of interest to the researchers was the knowledge gain (or, test score improvement), measured as the difference between the posttest and pretest scores. The sample mean knowledge gains for the three groups of students are provided in the next table.

a. The researchers theorized that as the level of homework assistance increased, the test score improvement from pretest to posttest would decrease. Do the sample means reported in the table support this theory?

b. What is the problem with using only the sample means to make inferences about the population mean knowledge gains for the three groups of students?

c. The researchers conducted a statistical test of hypothesis to compare the mean knowledge gain of students in the “no solutions” group with the mean knowledge gain of students in the “check figures” group. Based on the theory, part a, set up the null and alternative hypotheses for the test.

d. The observed significance level of the t-test of part c was reported as .8248. Using α = .05, interpret this result.

e. The researchers conducted a statistical test of hypothesis to compare the mean knowledge gain of students in the “completed solutions” group with the mean knowledge gain of students in the “check figures” group. Based on the theory, part a, set up the null and alternative hypotheses for the test.

f. The observed significance level of the t-test of part e was reported as .1849. Using α = .05, interpret this result. 

g. The researchers conducted a statistical test of hypothesis to compare the mean knowledge gain of students in the “no solutions” group with the mean knowledge gain of students in the “completed solutions” group. Based on the theory, part a, set up the null and alternative hypotheses for the test.

h. The observed significance level of the t-test of part g was reported as .2726. Using α = .05, interpret this result.

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Sample Size Sample Mean No Solutions 30 2.43 Check Figures 25 2.72 Completed Solutions 20 1.95