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. 2023 Jan 10;20(2):99–110. doi: 10.1177/17407745221146987

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© The Author(s) 2023

This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/en-us/nam/open-access-at-sage).

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Figure 2. — Graphical representations of different types of partially clustered trials. Each panel represents a two-arm trial with the left and right sides of the solid line depicting the two treatment arms. Each dot represents an observation. Dots grouped together in a circle/ellipse represent a cluster of correlated observations. Ungrouped dots represent the independent observations. (a) Individual randomisation with post-randomisation clustering. (b) Individual randomisation within pre-existing clusters. (c) Cluster randomisation of pre-existing clusters. (d) Balanced randomisation within pre-existing clusters.