Comments on the development of an oral health-related
self-efﬁcacy scale for use with older adults
We read the article by Ohara et al. with great interest.
Although the results were very interesting, there is an
important methodological issue that needs to be raised
in order to avoid misinterpretation.
The authors developed and validated the Geriatric
Self-Efﬁcacy Scale for Oral Health questionnaire on the
Here, is it crucial to emphasize that
developing and validating a questionnaire on the same
dataset can lead to over optimistic estimates of validity
of the questionnaire. In other words, estimates of valid-
ity of the questionnaire might suffer from an overﬁtting
problem; that is, performance of the questionnaire is
well described only for the observed data, but its per-
formance is still not valid for new and independent
subjects. Split sampling is a commonly used method
for questionnaire development and validation so that
the dataset is split into two parts, one part for develop-
ing and the other for validation.
In other words, in
one part of the dataset the construct of the question-
naire will be identiﬁed by exploratory factor analysis,
and in the reminder, its validity will be tested by conﬁr-
matory factor analysis.
The authors recruited a
remarkable sample size (n = 646 Japanese older people)
for the study; however, we are wondering why the
authors did no attempt to split the dataset and to deter-
mine the validity of the Geriatric Self-Efﬁcacy Scale for
Oral Health questionnaire in the proper way.
A take home message for readers is that question-
naire development and validation on the same dataset
is a common mistake in biomedical research.
This work was not supported by any organization.
The authors declare no conﬂict of interest.
and Saeid Saﬁri
Social Determinants of Health Research Center, Kurdistan
University of Medical Sciences, Sanandaj,
Epidemiology, School of Public Health, Iran University of Medical
Department of Epidemiology & Biostatistics, School of
Public Health, Tehran University of Medical Sciences, Tehran,
Managerial Epidemiology Research Center, Department of
Public Health, School of Nursing and Midwifery, Maragheh
University of Medical Sciences, Maragheh, Iran
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