Two graphs: a histogram and a Normal plot.
The histogram of cholesterol is positively skew. A Normal curve is superimposed which does not fit the histogram closely. At the lower end, the Normal curve remains above the axis where there are no cholesterol measurements. At the upper end, the Normal curve goes very close to the axis where there are cholesterol measurements. There are too many measurements to match the curve at the high cholesterol end.
The Normal plot shows Inverse Normal on the horizontal axis and serum cholesterol on the vertical axis. The Normal plot shows the points to be clearly higher than the straight line both at the low value and the high value end, but not in the middle.
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This page maintained by Martin Bland.
Last updated: 2 August, 2006.