Capítulo 2 El congreso de los Estados Unidos
2.1 El bicameralismo de Estados Unidos
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Psychological testing is essentially a twentieth-century phenomenon. With the rise of science and the use of mathematics in the nineteenth century, hope was raised that mathematical models could be harnessed to understand and explain man and to make predictions about him. The hope is that, through the use of mathematics, psychological tests can be developed that will use a small sample of man’s behavior (as exhibited on the test) to reveal a great deal more about him.
In her book Psychological Testing, Dr. Anne Anastasi gives a general definition of a psychological test. She says:
A psychological test is essentially an objective and standardized measure of a sample of behavior.1
The test is an attempt to diagnose some broad and significant aspect of an individual’s behavior in order to reveal something about him or to predict how he will perform in the future. Anastasi says:
Traditionally, the function of psychological tests has been to measure differences between individuals or between reactions of the same individual on different occasions.2
Numerous tests and types of tests have been developed to measure these differences. Psychologi-cal tests can be categorized under the following three general headings: 1) tests of general intellectual level, 2) tests of separate abilities, and 3) personality tests.
Our primary concern is with the last category, which includes personality inventories and temperament tests. However, before we go into detail, it is neces-sary to introduce two psychological testing features which are extremely important: reliability and valid-ity.
Every psychological test has numerous important features of construction and use. We will only describe two of them: reliability and validity. As we discuss those two terms in particular and later apply them to personality testing specifically, we will simplify as much as possible. Our goal in this chapter is to make this complex subject as clear as possible to help the reader understand the issues presented in the next chapter.
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The first term, reliability, refers to consistency.
Anastasi says:
Test reliability is the consistency of scores obtained by the same persons when retested with the identical test or with an equivalent form of the test.3
For example, if an individual takes an IQ test on Monday and Friday of the same week and receives IQ scores of 90 and 91 respectively, it is obvious that there is consistency between the two scores and that some confidence may be placed in the results.
If test/retest consistency happens often enough, with enough individuals, we will gain more and more confidence in the test’s reliability. However, if an individual takes an IQ test on Monday and Friday of the same week and scores 90 and 120 respectively, the inconsistency of scores indicates a lack of reli-ability and no confidence can be taken in either score.
The more often test/retest inconsistency occurs the less confidence one can take in the reliability of the test.
The minimum requirement for a test is that it must demonstrate reliability over time. However, reliability alone is not enough. Even if a test is highly reliable (consistent) it may still lack meaning. In other words, it may be consistent, but it may be consistently wrong. That is why the term reliable may be a bit misleading. A test that is reliable in terms of consis-tency may not be reliable in terms of accuracy or in
terms of giving the information it is designed to give.
For example, an individual may score at or near 90 on several administrations of an intelligence test, but really be far more intelligent by other measures.
In addition to being reliable, a test result must also be valid. Anastasi says: “The validity of a test concerns what the test measures and how well it does so.”4 (Emphasis hers.) She also says: “Undoubtedly the most important question to be asked about any psychological test concerns its validity.”5
While reliability means consistency of test results, validity can be thought of as the integrity of the test results. While reliability can be measured by comparing repeated results by the same individual on the same test (or an equivalent form), validity is best measured by comparing the test result with an independent, objective standard. We offer the follow-ing example to clarify these two concepts.
Let’s say an individual takes a computer typing test one day a week for three consecutive weeks and each time scores approximately 30 words per minute.
The reliability is excellent thus far. Let’s say that he takes the same test for three more weeks and scores about 30 words per minute each time. The reliability is better yet. If we add more individuals with simi-larly consistent results based upon various individual typing speeds, we are led to greater and greater confidence in the test’s reliability. However, we said earlier that a test could be reliably wrong.
While reliability is important, validity is far more important. Lack of validity on a test would
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strate that even though that particular test may be reliable, it should not be trusted.
Validity, at its best, involves some external, objec-tive standard against which to compare test results.
If, in the typing test example, we had an external, objective standard against which to measure, we could then judge the test results. What if the typist who consistently scored 30 words per minute on the typing test also typed at a computer at work? And, what if the computer had a software package that measured his typing speed and that software consistently showed that he generally typed approximately 60 words per minute? The typing test would be reliable for this individual, but not valid because of the great discrepancy between the typing test results and the external results from his software package at work.
Likewise if a substantial discrepancy existed for a large group of individuals, then the use of the test would be questionable.
In the next two chapters we will be dealing with this most important characteristic of validity, which is most ideally obtained by comparing results on the same test (or an equivalent form) with an external, objective criterion. We will be looking for this most important characteristic of validity as we examine personality inventories and temperament tests.