Evaluation of Instruction

In Evaluation of instruction by Peter K. Gessner [11 May 1973, p. 569], sentence 4, paragraph 2, column 1, should read as follows: It would seem likely that such an evaluative device would not differentiate between students able to solve the first problem presented to them and those who, although they may have been able to solve the fifth problem variant presented to them, failed to solve the first four.