Item Analysis in NCSS

NCSS includes Item Analysis and Item Response Analysis tools. Use the links below to jump to the item analysis topic you would like to examine. To see how these tools can benefit you, we recommend you download and install the free trial of NCSS.

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Though the names are similar, Item Analysis and Item Response Analysis are not the same. Item analysis studies the internal reliability of a test, survey or questionnaire. Item response analysis is used to analyze questions on a test that can be scored as either right or wrong to determine how well they discriminate between individuals of varying ability.

Technical Details

This page is designed to give a general overview of the capabilities of NCSS for item and item response analysis. If you would like to examine the formulas and technical details relating to a specific NCSS procedure, click on the corresponding ‘[Documentation PDF]’ link under each heading to load the complete procedure documentation. There you will find formulas, references, discussions, and examples or tutorials describing the procedure in detail.

Item Analysis

[Documentation PDF]

Item analysis studies the internal reliability of a particular instrument (test, survey, questionnaire, etc.). This instrument usually consists of several questions (items) which are answered by a group of respondents. Issues that arise include whether the instrument measures what was intended (e.g. Does a particular IQ test reliably measure an individual’s intelligence?), whether it produces the same results when it is administered repeatedly, whether it contains cultural biases, and so on.

Sample Data

Item Analysis - Sample Data

Procedure Input

Item Analysis - Procedure Window

Sample Output

Item Analysis - Sample Output

Item Response Analysis

[Documentation PDF]

Item response analysis is concerned with the analysis of questions on a test which can be scored as either right or wrong. The goal of item response analysis is to determine how well questions on a test discriminate between individuals of varying ability.

Sample Output

Item Response Analysis - Sample Output

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