A self-administrated questionnaire for the diagnosis of the most common headache disorders ensures standardization [1], but validation of the diagnostic instrument is required in epidemiological surveys to assess the precision of questionnaire diagnoses [1 3].
Table 7 shows the discriminating ability and precision of the questionnaire for several cut-off points of the total score for either sex separately and for the total sample.
By forming the testlets, we were able to capitalize on the accuracy of the subscales, while capitalizing on the precision of the full questionnaire to provide more information about an individual's level of knee symptoms-related experiences.
In spite of the slightly lower precision of the 6-item questionnaire in comparison with the original, the PGWB-S came out to be a robust instrument, suitable as a generic measure of HRQoL and a good tool for population surveys, where it can be easily administered.
In order to achieve this precision, 96 questionnaires would be needed for each of the four groups of older adults: living self reliantly, receiving homecare, living in nursing homes or having a legal guardian.
We might have underestimated their effect relative to that of body mass index because this is measured with greater precision than questionnaire based diet and physical activity assessment.
Translations of questionnaires were made into local languages when necessary, with back translation to ensure precision.
Adjustments were also made to increase the clarity and precision of the Italian version of the questionnaire.
Hence, if an IRT model fits the data coming from some QoL questionnaire well, the precision of the estimated effect size using this model might be higher than the one provided using CTT analysis.
We anticipated a 60% response rate, or 420 returned questionnaires, which would allow precision of within 5%, assuming the proportion that used HBPM was 10%.
Thousands of questionnaires were sent to managers across the country.
