Which method of assessing reliability is used to determine the reliability of a single test given on a single occasion?
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What is Reliability?By Dr. Saul McLeod, published 2013
For example, if a person weighs themselves during the course of a day they would expect to see a similar reading. Scales which measured weight differently each time would be of little use. The same analogy could be applied to a tape measure which measures inches differently each time it was used. It would not be considered reliable. If findings from research are replicated consistently they are reliable. A correlation coefficient can be used to assess the degree of reliability. If a test is reliable it should show a high positive correlation. Of course, it is unlikely the exact same results will be obtained each time as participants and situations vary, but a strong positive correlation between the results of the same test indicates reliability. There are two types of reliability – internal and external reliability.
Assessing ReliabilitySplit-half methodThe split-half method assesses the internal consistency of a test, such as psychometric tests and questionnaires. There, it measures the extent to which all parts of the test contribute equally to what is being measured. This is done by comparing the results of one half of a test with the results from the other half. A test can be split in half in several ways, e.g. first half and second half, or by odd and even numbers. If the two halves of the test provide similar results this would suggest that the test has internal reliability. The reliability of a test could be improved through using this method. For example, any items on separate halves of a test which have a low correlation (e.g. r = .25) should either be removed or re-written. The split-half method is a quick and easy way to establish reliability. However, it can only be effective with large questionnaires in which all questions measure the same construct. This means it would not be appropriate for tests which measure different constructs.
Test-retestThe test-retest method assesses the external consistency of a test. Examples of appropriate tests include questionnaires and psychometric tests. It measures the stability of a test over time. A typical assessment would involve giving participants the same test on two separate occasions. If the same or similar results are obtained then external reliability is established. The disadvantages of the test-retest method are that it takes a long time for results to be obtained.
The timing of the test is important; if the duration is to brief then participants may recall information from the first test which could bias the results. Alternatively, if the duration is too long it is feasible that the participants could have changed in some important way which could also bias the results. Inter-rater reliabilityThe test-retest method assesses the external consistency of a test. This refers to the degree to which different raters give consistent estimates of the same behavior. Inter-rater reliability can be used for interviews. Note, it can also be called inter-observer reliability when referring to observational research. Here researchers observe the same behavior independently (to avoided bias) and compare their data. If the data is similar then it is reliable. Where observer scores do not significantly correlate then reliability can be improved by:
How to reference this article:How to reference this article:McLeod, S. A. (2007). What is reliability? Simply Psychology. www.simplypsychology.org/reliability.html APA Style ReferencesBeck, A. T., Steer, R. A., & Brown, G. K. (1996). Manual for the beck depression inventory The Psychological Corporation. San Antonio, TX. Hathaway, S. R., & McKinley, J. C. (1943). Manual for the Minnesota Multiphasic Personality Inventory. New York: Psychological Corporation.
Home | About Us | Privacy Policy | Advertise | Contact Us Simply Psychology's content is for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. © Simply Scholar Ltd - All rights reserved Which methods is used for determining reliability of a test?Three important methods for estimating test reliability are (1) method of parallel forms, (2) test-retest method, (3) split-half method.
What is the most commonly used method of assessing reliability?The most common way to measure parallel forms reliability is to produce a large set of questions to evaluate the same thing, then divide these randomly into two question sets. The same group of respondents answers both sets, and you calculate the correlation between the results.
What are 3 types of reliability assessments?Reliability refers to the consistency of a measure. Psychologists consider three types of consistency: over time (test-retest reliability), across items (internal consistency), and across different researchers (inter-rater reliability).
What are the two methods of reliability?There are two types of reliability – internal and external reliability. Internal reliability assesses the consistency of results across items within a test. External reliability refers to the extent to which a measure varies from one use to another.
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