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. 2013 Mar 15;9(3):217–225. doi: 10.5664/jcsm.2482

Figure 4. Bland-Altman plots of whole-night sleep outcomes.

Figure 4

The graphs show the difference between actigraphy and PSG (actigraphy value – PSG value) plotted against the mean of actigraphy and PSG on each of the sleep outcome: total sleep time (A), sleep efficiency (B), wake after sleep onset (C), and sleep latency (D). The horizontal reference line represents zero difference between the two recording methods on each outcome. Values above the zero-difference line indicate higher values on actigraphy than PSG (i.e., overestimation by actigraphy); values below the zero-difference line indicate lower values on actigraphy than PSG (i.e., underestimation by actigraphy).