Relation between Validity and Reliability of a Test
After reading this article you will learn about the relation between validity and reliability For example, when a man wrongly reports his date of birth consistently. Reliability and validity are important concepts within psychometrics. need not be any necessary relationship between the two. For example, a valid measure of suicide intention. Nov 8, Though reliability and validity are different from each other, they are still related. and you want to study the relationship between stereotyped thinking and For example, if your scale read '' every single time you stepped.
RELIABILITY AND VALIDITY
Consistency is partly ensured if the attribute being measured is stable and does not change suddenly. However, errors may be introduced by factors such as the physical and mental state of the examinee, inadequate attention, distractedness, response to visual and sensory stimuli in the environment, etc.
When estimating the reliability of a measure, the examiner must be able to demarcate and differentiate between the errors produced as a result of inefficient measurement and the actual variability of the true score.
A true score is that subset of measured data that would recur consistently across various instances of testing in the absence of errors.
Hence, the general score produced by a test would be a composite of the true score and the errors of measurement. Types of Reliability Test-retest Reliability It is a measure of the consistency of test results when the test is administered to the same individual twice, where both instances are separated by a specific period of time, using the same testing instruments and conditions.
The two scores are then evaluated to determine the true score and the stability of the test. This type is used in case of attributes that are not expected to change within that given time period.
This works for the measuring of physical entities, but in the case of psychological constructs, it does exhibit a few drawbacks that may induce errors in the score.
Relation between Validity and Reliability of a Test
Firstly, the quality being studied may have undergone a change between the two instances of testing. Secondly, the experience of taking the test again could alter the way the examinee performs. And lastly, if the time interval between the two tests is not sufficient, the individual might give different answers based on the memory of his previous attempt. Example Medical monitoring of "critical" patients works on this principle since vital statistics of the patient are compared and correlated over specific-time intervals, in order to determine whether the patient's health is improving or deteriorating.
Depending on which, the medication and treatment of the patient is altered. Parallel-forms Reliability It measures reliability by either administering two similar forms of the same test, or conducting the same test in two similar settings. Despite the variability, both versions must focus on the same aspect of skill, personality, or intelligence of the individual. The two scores obtained are compared and correlated to determine if the results show consistency despite the introduction of alternate versions of environment or test.
However, this leads to the question of whether the two similar but alternate forms are actually equivalent or not. Example If the problem-solving skills of an individual are being tested, one could generate a large set of suitable questions that can then be separated into two groups with the same level of difficulty, and then administered as two different tests.
The comparison of the scores from both tests would help in eliminating errors, if any.
Understanding Assessment: Reliability and Validity
Inter-rater Reliability t measures the consistency of the scoring conducted by the evaluators of the test. It is important since not all individuals will perceive and interpret the answers in the same way, hence the deemed accurateness of the answers will vary according to the person evaluating them.
This helps in refining and eliminating any errors that may be introduced by the subjectivity of the evaluator. If a majority of the evaluators judge are in agreement with regards to the answers, the test is accepted as being reliable. But if there is no consensus between the judges, it implies that the test is not reliable and has failed to actually test the desired quality. However, the judging of the test should be carried out without the influence of any personal bias.
In other words, the judges should not be agreeable or disagreeable to the other judges based on their personal perception of them. Example This is often put into practice in the form of a panel of accomplished professionals, and can be witnessed in various contexts such as, the judging of a beauty pageant, conducting a job interview, a scientific symposium, etc.
Internal Consistency Reliability It refers to the ability of different parts of the test to probe the same aspect or construct of an individual.
If two similar questions are posed to the examinee, the generation of similar answers implies that the test shows internal consistency. If the answers are dissimilar, the test is not consistent and needs to be refined. It is a statistical approach to determine reliability. It is of two types. Finally, an average is calculated of all the correlation coefficients to yield the final value for the average inter-item correlation. In other words, it ascertains the correlation between each question of the entire test.
Concept of Validity It refers to the ability of the test to measure data that satisfies and supports the objectives of the test. It refers to the extent of applicability of the concept to the real world instead of a experimental setup. With respect to psychometrics, it is known as test validity and can be described as the degree to which the evidence supports a given theory.
It is important since it helps researchers determine which test to implement in order to develop a measure that is ethical, efficient, cost-effective, and one that truly probes and measures the construct in question. Other non-psychological forms of validity include experimental validity and diagnostic validity. Experimental validity refers to whether a test will be supported by statistical evidence and if the test or theory has any real-life application.
Diagnostic validity, on the other hand, is in the context of clinical medicine, and refers to the validity of diagnostic and screening tests. Types of Validity Construct Validity It refers to the ability of the test to measure the construct or quality that it claims to measure, i. Reliability is concerned with the stability of test scores-self correlation of the test. Every reliable test is not necessarily valid.
A test having high correlation with itself may not have equally high correlation with a criterion. Reliability is a prerequisite of validity. A highly reliable test is always a valid measure of some function. Thus, reliability controls validity. Reliability may be said as the dependability of measurement. Maximum reliability is found in case of homogeneous items. Maximum reliability requires items of equal difficulty and high inter- correlation among test items.
Validity co-efficient does not exceed the square root of reliability coefficient. The reliability is the proportion of true variance. We cannot claim that a reliable test is also valid. This may or may not be true. A test measures consistently, but it may not measure what it intends to measure.
For example, when a man wrongly reports his date of birth consistently, it may be reliable but not valid. Relation Validity of a Test: Validity is concerned with the extent to which the purpose of the test is being served.
- The Concepts of Reliability and Validity Explained With Examples
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It studies how truthfully the test measures what it purports to measure.