15.51 Having carried out the study of Exercise 15.34, the instructor decided to replicate the study the following year. The results obtained are shown in the table.

Combining these results with those of Exercise 15.34, carry out the analysis of variance calculations and discuss your findings.

Text Examination A B C Multiple choice 4.7 5.1 4.8 Essays 4.4 4.6 4.0 Mix 4.5 5.3 4.9