What does Reliability mean?
Test reliability is the accuracy with which a given score for a given individual person measures the trait in question. For a score to be reliable the person must take the test carefully and conscientiously. As far as the test itself is concerned, good reliability can be assured if the test questions are carefully written and there are enough of them. For some traits, 30 questions are desirable. For other traits, only 6 or 10 questions are enough. For gender, age, years of education and high school grade point average, only one question each is enough. If we wish to measure several aspects of a trait, such as verbal, spatial and memory aspects of intelligence, we may need 30 questions for each aspect. If we plan to score a test using different norms for each of several age levels, then more than 30 questions may be necessary to obtain reliable measures for the full range of the trait at each age level. Well-designed tests include items which have been carefully crafted and have passed
