• Entry
  • Reader's guide
  • Entries A-Z
  • Subject index
icon backReturn to Entries

Item Information Function

In item response theory, the item information function is a measure of how much statistical information a test item provides. Item information is a function of θ, the ability, proficiency, skill, or trait measured by the examinee’s responses to the test items. Figure 1 shows the information functions for four items. Items 1 and 2 are more informative at low values of θ than high values, and Items 3 and 4 are most informative at higher values of θ.

Figure 1 Information for four items. Items 1 and 2 have the same difficulty but Item 1 is more discriminating. Items 3 and 4 are more difficult than Items 1 and 2. Item 4 has the same parameters as Item 3, except that the lower asymptote ...
    • Loading...
    locked icon

    Sign in to access this content

    Get a 30 day FREE TRIAL

    • Watch videos from a variety of sources bringing classroom topics to life
    • Read modern, diverse business cases
    • Explore hundreds of books and reference titles