One other point: If one or more tests of a year group have been omitted, as sometimes happens either from oversight or lack of time, the question arises how the tests which were given in such a year group should be evaluated. Suppose, for example, a subject has been given only four of the six tests in a given year, and that he passes two, or half of those given. In such a case the probability would be that had all six tests been given, three would have been passed; that is, one half of all. It is evident, therefore, that when a test has been omitted, a proportionately larger value should be assigned to each of those given. If all six tests are given in any year group below XII, each has a value of 2 months. If only four are given, each has a value of 3 months (12 ÷ 4 = 3). If five tests only are given, each has a value of 2.4 months (12 ÷ 5 = 2.4). If in year group XII only six of the eight tests are given, each has a value of 4 months (24 ÷ 6 = 4). If in the "average adult" group only five of the six tests are given, each has a value of 6 months instead of the usual 5 months. In this connection it will need to be remembered that the six "average adult" tests have a combined value of 30 months (6 tests, 5 months each); also that the combined value of the six "superior adult" tests is 36 months (6 × 6 = 36). Accordingly, if only five of the six "superior adult" tests are given, the value of each is 36 ÷ 5 = 7.2 months. For example, let us suppose that a subject has been tested as follows: All the six tests in X were given and all were passed; only six of the eight in XII were given and five were passed; five of the six in XIV were given and three were passed; five of the six in "average adult" were given and one was passed; five were given in "superior adult" and no credit earned. The result would be as follows:-- _Years__Months_ Credit presupposed, years I to IX 9 Credit earned in X, 6 given, 6 successes 1 Credit earned in XII, 6 given, 5 passed. Unit value of each test given is 24 ÷ 6 = 4. Total value of the 5 tests passed is 5 × 4 or 1 8 Credit earned in XIV, 5 tests given, 3 passed. Unit value of each of the 5 given is 24 ÷ 5 = 4.8. Value of the 3 passed is 3 × 4.8, or 0 14+ Credit earned in "average adult," 5 tests given, 1 passed. Unit value of the 5 tests given is 30 ÷ 5 = 6. Value of the 1 success 0 6 Credit earned in "superior adult" 0 0 ---- ---- Total credit 13 4+