Validation and comparison study of three urbanicity scales in a Thailand context

Validity and reliability of an urbanicity scale is of utmost importance in developing effective strategies to minimize adverse social and health consequences of increased urbanization. A number of urbanicity scales for the quantitative assessment of the "static" feature of an urban environment has been invented and validated by the original developers. However, their comparability and robustness when utilized in another study context were not verified. This study aimed to examine the comparability, validity, and reliability of three urbanicity scales proposed by Dahly and Adair, Jones-Smith and Popkin, and Novak et al. in a Thailand context.

Urban characteristics data for 537 communities throughout Thailand were obtained from authoritative sources, and urbinicity scores were calculated according to the original developers' algorithms with some modifications to accommodate local available data. Comparability, dimensionality, internal consistency, and criterion-related and construct validities of the scores were then determined.

All three scales were highly correlated, but Dahly and Adair's and Jones-Smith and Popkin's were more comparable. Only Dahly and Adair's scale achieved the unidimensionality assumption. Internal consistency ranged from very poor to high, based on their Chonbach's alpha and the corrected item-scale correlation coefficients. All three scales had good criterion-related validity (when compared against the official urban-rural dichotomy and four-category urbanicity classification) and construct validity (in terms of their relation to the mean per capita monthly income and body mass index).

This study's results ensure the utility of these three urbanicity scales as valid instruments for examining the social and health impacts of urbanicity/urbanization, but caution must be applied with comparisons of urbanicity levels across different studies when different urbanicity scales are applied.