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# Inter-rater Reliability

## Reliability of Raters

Reliability of raters entails the consistency of a set of variables to assess the different types of scores' stability. The reliability index of a test score indicates its stability, which may imply the test-retest, internal consistency or inter-rater reliability. Testing reliability of raters can be done through inter-rater reliability where there is a level of agreement between raters (Kline, 2005). If all the raters agree, the IRR is 1, and if everyone disagrees, the IRR is 0. Although there are several methods to calculate the IRR including the percent agreement and Cohen’s Kappa, how the test is carried out significantly depends on the type of data being used and the numbers of in the model. For instance, to access percent agreement for two raters; the number of ratings in an agreement is counted followed by the total number of ratings, which is then divided by the number in agreement to get a fraction that is converted into a percentage and finally the assessment field helps determine the acceptable agreement level (Tinsley et al. 2015). Besides, other statistical methods, such as test-retest can also be applied where various personality test questions are tried out with a group of people over time to help determine better reliability.

## Types of Situations Where Different Types of Statistics Mentioned Would Be Used to Demonstrate Inter-Rater Reliability

Different types of situations may require a different kind of statistics to show IRR, for example, the results gathered while watching any sport used for personality tests depends entirely on human observers and maintaining consistency between them. If one of the assessors is unreliable in the scoring system, then the whole system can be jeopardized and deny the participants or test takers their rightful positions or assessments (Tinsley et al. 2015). Relatively, IRR has some far more significant implications and can directly influence people’s lives, for example, during examination marking or while administering personal evaluation questions. The examiners are regularly assessed to ensure that they follow the same standards such that everyone gets a fair chance.

## Examples of When Alternate Forms Reliability and Inter-Rater Reliability Would Be Used Most Often

The alternative forms approach was developed to overcome the challenge of carryover effects and situational changes to the test takers. The method requires the variables to be equal, parallel or across test versions. Thus, the alternative forms would mostly be used where a situation involves the primary concern of the question is the equality of variables (Kline, 2005). The IRT, for instance, produces the parameters of items that answers the question of test and item equality hence the reliability indices associated with them are reasonable. On the other hand, inter-rater reliability would be used most often when the raters are conducting tests to assess traits, such as personality and intelligence where the judges must establish IRR and ensure that the generated results will be useful (Epstein et al. 2009). For instance, while scaling the levels of aggression displayed by the test takers where the raters have to continually calibrate and compare their ratings while adjusting their scales to ensure the results are similar as possible.

## Summary

Summarizing, in statistics reliability indices are important aspects of test validity as they help obtain accurate score across a range of assessments and function as a substantial tool in psychological testing. Thus, it can be perceived as consistency or repeatability, which is mostly tested through inter-rater, test-retest or alternative form reliability methods. While the inter-rater reliability is most often applied in different situations, it is recommended to apply other methods like alternative forms reliability, especially when equality is the main concern.

## References

Epstein, M. H., Harniss, M. K., Pearson, N., " Ryser, G. (2009). The Behavioral and Emotional Rating Scale: Test-retest and inter-rater reliability. Journal of Child and Family Studies, 8(3), 319-327.

Kline, T. (2005). Psychological testing: A practical approach to design and evaluation. Thousand Oaks, CA: Sage Publications.

Tinsley, H. E., " Weiss, D. J. (2015). Interrater reliability and agreement of subjective judgments. Journal of Counseling Psychology, 22(4), 358.