The intelligence of an individual is assessed through measuring instrument called tests. Psychologists depend on intelligence tests, as these are very helpful to assess a person’s intellectual processes. A test must posse certain characteristics in order to yield meaningful information. A test has three basic requirements: reliability, validity, and standardization. If the test (does not possess any of these requirements, the assessment does not yield meaningful information.
If a test measures something consistently, then it is considered as reliable. Reliability means how consistently the person performs on a test. If a person’s performance on a test shows wide variations from one occasion to another, the test is not considered to be reliable. For example, a thermometer is said to be reliable if it records a value of 98.4 degrees Fahrenheit for the normal body temperature and a figure above 98.4 degrees for a person suffering from fever, and does so consistently.
If a thermometer records 98 degrees the first time, and 100.5 degrees the second time for the same body temperature, it is said to be unreliable. A ruler (scale) is a good physic measuring instrument for length, because it provides the same or consistent measurement index repeatedly. Similarly an intelligence test would be considered reliable, if it records relatively the same performance level eve time it is administered.
A test is said to be valid if it measures what it intends to measure. An intelligence test will be valid if it measures intelligence. If a testis valid, it will always be reliable. We should use valid tests of intelligence in order to make meaningful inferences about the intelligence status of an individual.
Standardization refers to the processes and procedures of establishing a set of norms for a test. In testing including intelligence, the investigator has to establish for a particular test a set of uniform procedure for its administration, the scoring techniques to be used, and the methods of evaluation and interpretation of the obtained score. Standardization involves thorough empirical analysis so that an adequate set of norms has been developed, and a reasonable assessment of its reliability and validity has been obtained.