Types of reliability in research

Inter-Rater Test-retest Parallel-forms Internal consistency See also 'Reliability' of any research is the degree to which it gives an accurate score across a range of measurement.

reliability statistics

If their research does not demonstrate that a measure works, they stop using it. In addition, we compute a total score for the six items and use that as a seventh variable in the analysis. Item response theory[ edit ] It was well known to classical test theorists that measurement precision is not uniform across the scale of measurement.

Methods of reliability

This helps the researcher determine those questions and combinations that have better reliability. Since this correlation is the test-retest estimate of reliability, you can obtain considerably different estimates depending on the interval. But if it indicated that you had gained 10 pounds, you would rightly conclude that it was broken and either fix it or get rid of it. You might use the test-retest approach when you only have a single rater and don't want to train any others. So how do we determine whether two observers are being consistent in their observations? However it can only be effective with large questionnaires in which all questions measure the same construct. OK, it's a crude measure, but it does give an idea of how much agreement exists, and it works no matter how many categories are used for each observation.

When you have only a few items, and therefore usually lower internal reliability, having a larger sample size helps offset the loss in reliability. Reactivity effects are also partially controlled; although taking the first test may change responses to the second test.

Test-retest Multiple researchers making observations or ratings about the same topic. The test that gives the most consistent results is used, whilst the other provided it is sufficiently consistent is used as a backup. We know that if we measure the same thing twice that the correlation between the two observations will depend in part by how much time elapses between the two measurement occasions.

Types of reliability ppt

If they cannot show that they work, they stop using them. But if it were found that people scored equally well on the exam regardless of their test anxiety scores, then this would cast doubt on the validity of the measure. This arrangement guarantees that each half will contain an equal number of items from the beginning, middle, and end of the original test. See an example Parallel forms reliability Parallel forms reliability measures the correlation between two equivalent versions of a test. Psychologists consider three types of consistency: over time test-retest reliability , across items internal consistency , and across different researchers inter-rater reliability. Note, it can also be called inter-observer reliability when referring to observational research. If the same or similar results are obtained then external reliability is established. Validity is a judgment based on various types of evidence. All these low correlations provide evidence that the measure is reflecting a conceptually distinct construct. For example, alternate forms exist for several tests of general intelligence, and these tests are generally seen equivalent. In this scenario it would be unlikely they would record aggressive behavior the same and the data would be unreliable. California: Mayfield Publishing Company. Item response theory[ edit ] It was well known to classical test theorists that measurement precision is not uniform across the scale of measurement. For each observation, the rater could check one of three categories.

This is done by comparing the results of one half of a test with the results from the other half. The variation in results from a standard gives a measure of their reliability.

validity in research

A perfectly reliable result would be that they both classify the same pictures in the same way. One major problem with this approach is that you have to be able to generate lots of items that reflect the same construct.

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What is Reliability?