Graph description: Figure 3. Difference against mean for PEFR data, with mean difference and mean 2SD marked

This is a scatter diagram, showing average P E F R by the two meters on the horizontal axis and the difference in P E F R, Wright meter minus mini meter, on the vertical axis. The vertical and horizontal scales have similar sized intervals representing 100. The horizontal scale is labeled 200, 300, 400, 500, 600, 700 litres per minute. The vertical scale is labeled minus 100, minus 50, 0, 50, and 100 litres per minute.

There are three horizontal lines on the graph, approximately through minus 80, 2, and 76. The lowest line is labeled mean minus 2 S D, the middle line is labeled mean, the highest line is labeled mean plus 2 S D.

The points form a horizontal cloud with the centre at about 450 horizontally and 0 vertically. There is an outlier at about average = 220, difference = minus 80 litres per minute.

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This page maintained by Martin Bland.
Last updated: 29 April, 2008.