Newtonian Gravity Concept Inventory (NGCI)

Developed by Kathryn Williamson and Shannon Willoboughby

Purpose To assess introductory general education college astronomy (“Astro 101”) students’ understanding of Newtonian gravity.
Format Pre/post, Multiple-choice
Duration 20 min
Focus Astronomy Content knowledge (directionality of gravity, force law, thresholds related to gravity, independence of forces)
Level Intro college
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Sample questions from the NGCI:

NGCI Implementation and Troubleshooting Guide

Everything you need to know about implementing the NGCI in your class.

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K. Williamson, S. Willoughby, and E. Prather, Development of the Newtonian Gravity Concept Inventory, Astron. Educ. Rev. 12 (1), 1 (2013).
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Silver Validation
This is the second highest level of research validation, corresponding to at least 5 of the validation categories below.

Research Validation Summary

Based on Research Into:

  • Student thinking

Studied Using:

  • Student interviews
  • Expert review
  • Appropriate statistical analysis

Research Conducted:

  • At multiple institutions
  • By multiple research groups
  • Peer-reviewed publication

The multiple-choice questions on the NGCI were developed based on previous research on student ideas about gravity. The authors started with concept map with four aspects of gravity (concept domains), which were used to create the initial set of test questions. The questions underwent several rounds of testing and revision, which consisted of giving the questions to students and analyzing the responses, student interviews and expert review. Appropriate statistical analysis of reliability, difficulty and discrimination were conducted and reasonable values found. A wide range of normalized gain scores were found for different courses, indicating that that NGCI is sensitive to differences in instruction. The NGCI has been used with over 900 students at six institutions and results are published in one peer-reviewed publication.


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Language Translator(s)  
Arabic Hisham Bani-Salameh

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Typical Results

Typical scores on the NGCI as given in Table 2 of Williamson and Willoughby 2013:

The latest version of the NGCI, released in 2013, is version 3.