Advantages and Limitations Of Classical Test Theory.
Before looking at the advantages and the limitations of classical test theory (CTT), let’s briefly understand the concept of classical test theory.
Classical test theory is the body of concepts and methods that have formed the basis of psychological assessment. The theory assumes that each observed score (X) is a combination of an underlying true score (T) on the concept of interest and random error (E).
Classical test theory, also known as true score theory, assumes that each person has a true score, T, that would be obtained if there were no errors in measurement. A person’s true score is defined as the expected score over an infinite number of independent administrations of the scale. Scale users never observe a person’s true score, only an observed score, X.
Classical test theory assumes that the observed scores are the additive function of the true scores and error terms.
That is, X = T + E, where
X: is the observed score
T: is the true score
E: is the error
True scores are the ideal value of a construct in a particular person or situation. The error term is the effect of factors extraneous to the construct of interest. Error terms are assumed to be independent of (or uncorrelated with) the true scores.
Manipulation of elements hypothesized to influence the error term can be used to investigate the reliability of a score.
A test could, for example, be given to the same persons on two distinct days to assess the effect of elements connected to time or measurement instance.
The magnitude of the error term and the proportion can be estimated using the relationship between the two observed scores, which can be obtained using a correlation coefficient or an analysis of variance.
Advantages of Classical Test Theory
The classical test theory is a straightforward and practical concept that explains how measurement errors might affect observed results. We’ll look at some of the benefits of classical test theory.
- Classical test theory is used to quantify measurement error and solve related problems including adjusting observed variable dependencies for attenuation owing to measurement errors.
- CTT is used to understand and improve the reliability of psychological tests.
- The Classical test theory is concerned with the relations between the three variables. X, T and in the population. These relations are used to draw inference about the quality of test scores.
- Classical test theory has a traditional quantitative approach to testing the reliability and validity of a scale based on its items.
- Classical test theory is used across populations.
Despite the advantages or importance of classical test theory, the theory is not without its limitations.
Limitations of Classical Test Theory
Separation: One of the most well-known flaws of classical test theory (CTT) is that examinee and test characteristics are inextricably linked, meaning that each can only be evaluated in the context of the other.
Reliability: The second flaw is the standard test theory definition of reliability, which stipulates that reliability is “the correlation between test scores on parallel forms of a test.”
The issue here is that different people have different ideas about what parallel tests are. Various reliability coefficients provide lower limit estimates of reliability as well as estimations of reliability with unknown biases.
Standard Error of Measurement: The issue here is that, according to traditional test theory, every examinees’ standard error of measurement is considered to be the same.
Test Oriented: Another flaw in Classical test theory is that it focuses on the test rather than the items. Classic test theory, to put it another way, cannot assist us forecast how well an individual or even a group of examinees would perform on a test item.
Finally, once the item stems have been developed and subjected to expert content analysis. They are frequently removed from the analysis process. Individuals may report that a particular item stem is biased or ambiguous. But there are no statistical processes in CTT that allow for comparisons of item content or stimulus.
Classical test theory is a simple and useful model that discusses how errors of measurement can influence the observed scores which is used to quantify measurement error and to solve related problems such as correcting observed dependencies between variables for the attenuation due to measurement errors.