Rating scale categories should be well defined, mutually exclusive, univocal and exhaustive (J.P. Guilford), but this is not enough. They must also be clearly differentiated in the behavior of the respondents, otherwise more categories do not mean more information. Here is an apparently well constructed scale:
How much do you fear...
1. Not at all
2. A little
3. Somewhat
4. More
5. A lot
But could the respondents clearly discriminate 5 levels of fear? The plot shows the statistical separation of the respondents obtained when adjacent categories are clumped together. Person separation is best with the categories grouped into 3 levels, and one of the dichotomizations is almost as good as the original five category scale. The choice of scoring model can dramatically alter results. The statistically best scoring model for these data was:
How much do you fear...
1. Not at all
2. A little
3. Somewhat, More, A lot
Mark Stone & Ben Wright
Maximizing rating scale information. Stone MH, Wright BD. Rasch Measurement Transactions, 1994, 8:3 p.386
Forum | Rasch Measurement Forum to discuss any Rasch-related topic |
Go to Top of Page
Go to index of all Rasch Measurement Transactions
AERA members: Join the Rasch Measurement SIG and receive the printed version of RMT
Some back issues of RMT are available as bound volumes
Subscribe to Journal of Applied Measurement
Go to Institute for Objective Measurement Home Page. The Rasch Measurement SIG (AERA) thanks the Institute for Objective Measurement for inviting the publication of Rasch Measurement Transactions on the Institute's website, www.rasch.org.
Coming Rasch-related Events | |
---|---|
Oct. 4 - Nov. 8, 2024, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
Jan. 17 - Feb. 21, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
May 16 - June 20, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
June 20 - July 18, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Further Topics (E. Smith, Facets), www.statistics.com |
Oct. 3 - Nov. 7, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
The URL of this page is www.rasch.org/rmt/rmt83r.htm
Website: www.rasch.org/rmt/contents.htm