Presentation on theme: "Types of Reliability. Reliability of Consistency of What? l Observers or raters l Tests over time l Different versions of the same test l A test at one."— Presentation transcript:
Types of Reliability
Reliability of Consistency of What? l Observers or raters l Tests over time l Different versions of the same test l A test at one point in time
Inter-Rater or Inter-Observer Reliability Object or phenomenon
Inter-Rater or Inter-Observer Reliability Observer 1 Object or phenomenon
Inter-Rater or Inter-Observer Reliability Observer 1 Observer 2 Object or phenomenon
Inter-Rater or Inter-Observer Reliability Observer 1 Observer 2 Object or phenomenon = ?
Inter-Rater or Inter-Observer Reliability l Are different observers consistent? l Can establish this outside of your study in a pilot study. l Can look at percent of agreement (especially with category ratings). l Can use correlation (with continuous ratings).
Test-Retest Reliability Time 1 Time 2
Test-Retest Reliability TestTest Time 1 Time 2 =
Test-Retest Reliability TestTest Time 1 Time 2 = Stability over time
Test-Retest Reliability l Measure instrument at two times for multiple persons. l Compute correlation between the two measures. l Assumes there is no change in the underlying trait between time 1 and time 2.
Parallel-Forms Reliability Time 1 Time 2
Parallel-Forms Reliability Form B Time 1 Time 2 Form A =
Parallel-Forms Reliability Form B Time 1 Time 2 Stability across forms Form A =
Parallel-Forms Reliability l Administer both forms to the same people. l Get correlation between the two forms. l Usually done in educational contexts where you need alternative forms because of the frequency of retesting and where you can sample from lots of equivalent questions.
Internal Consistency Reliability Average inter-item correlation
Internal Consistency Reliability Test Average Inter-Item Correlation
Internal Consistency Reliability Test Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Average Inter-Item correlation