Four graphs, a histogram of ulcer area, a Normal plot for ulcer area, a histogram of log 10 ulcer area, a Normal plot for log 10 ulcer area.

The histogram of ulcer area shows great positive skewness. The tallest bar is on the extreme left.

The Normal plot of ulcer area has ulcer area on the vertical axis and Inverse Normal on the horizontal axis. The line of points curves upwards very strongly. The points are above the straight line of perfect Normal distribution for low ulcer area, and at the low ulcer area end the line of points is horizontal. The line of points goes below the straight line in the middle of the range of ulcer area, where it bends sharply and then rises steeply above the straight line for high ulcer areas.

The histogram of log 10 ulcer shows a small amount of positive skewness. The tallest bar is the third of the six bars in this histogram.

The Normal plot of log ulcer area has log ulcer area on the vertical axis and Inverse Normal on the horizontal axis. The line of points curves upwards very gently. The points are just above the straight line of perfect Normal distribution for low log ulcer area, just below the line in the middle of the range of log ulcer area, and above the line for high log ulcer areas.

Back to Clinical Biostatistics: Transformations.

This page maintained by Martin Bland.

Last updated: 3 August, 2006.