ABSTRACT
Objectives:To investigate appropriate approach of testing the interval feature of alternative answers in questionnaires.Methods:We calculated the total scores of the items within the same domain excluding the item that was under test, and then, identified the distances between the scores of the population who chose the different alternative answers of the test item. The short form 36 was used in the test. We surveyed a total of 2250 residents, with 2246 included in the final analysis.Results:This approach could find the deviated item in the questionnaire. The results of testing of the interval feature of alternative answers were consistent with the original design; however, the clustered items must have good construct validity.Conclusion:Using the items clustered in one domain to test the interval feature of alternative answers may possibly be an available simple approach, but we need more mathematics evidence to prove this assumption.