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Figure 3 | International Journal of Behavioral Nutrition and Physical Activity

Figure 3

From: Categorisation of built environment characteristics: the trouble with tertiles

Figure 3

Illustration that within a meta-analysis the tertile approach will tend to a linear model. The SESAW data [3] were split into 20 sub-samples (A-T), each with nā€‰=ā€‰75. This plot shows four meta-analyses which combine an increasing number of the sub-samples (A, A-G, A-M, and A-T). The linear model approach is consistent and approaches the equivalent analysis using the full data. Conversely, the tertile approach becomes increasingly bumpy, as each sub-sample has data-dependent tertile cut-points. In the limit, as illustrated, the tertile combined analysis will tend towards the linear model approach.

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