X1.2.1 Repeatability (r)-The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method exceed the following values only in one case in twenty. Repeatability (r) may be calculated as shown in Eq X1.5 for the five gasoline samples. See Table X1.2 for calculated values and Fig. X1.2 for data plots.