Deviations from standard test methods may cause good concrete to be rejected or poor concrete to be accepted. Either result is undesirable. The details of test methods may appear to be unimportant, even arbitrary. The key word is uniformity. Without uniformity in testing methods--always doing the tests in the same way--test results can't fulfill their purpose, which is to detect changes in the concrete that could affect performance. Different test results could simply reflect differences in the way the test was run.