1. Length of test - generally, the longer the test, the larger the reliability coefficient.

2. Range of variability in scores - the larger the range of scores, the higher the reliability.

3. Guessing - when the probability of guessing correct answers increases, the reliability of the test decreases. Therefore, usually true or false tests have less reliability than multiple choice and they, in turn, have lesser reliability than free-recall tests, with all other factors remaining the same.

4. Interpretation of reliability coefficient - a reliability coefficient of .84 indicates that 84 % of the variability of the test scores was due to true score differences between exams, and the other 16% was due to measurement error. Usually, a reliability coefficient of .80 and above is acceptable.