Two graphs, a histogram with a superimposed Normal curve and a Normal plot.

The histogram has "Systolic BP (mm Hg)" on the horizontal axis numbered 0, 100, 200 and 300. The vertical axis is labeled "Frequency" and numbered 0, 20, 40, and 60.

The histogram is bimodal with modes at systolic BP = 100 to 120, frequency = 55 and at systolic BP = 160 to 180, frequency = 35. Betwen 120 and 160 the frequencies are below 20. There are bars with non-zero frequency between 40 and 260. The Normal distribution does not fit the distribution well and has frequency above zero at systolic BP = zero.

The Normal plot has Systolic BP on the vertical axis and Inverse Normal on the horizontal axis. The line of points is not close to the straight line of perfect Normal distribution. The line of points starts above the straight line of perfect Normal distribution, then falls below it, then rises above the line, then falls below it again and finally runs along it for the last few cases.

Back to Clinical Biostatistics: Transformations.

This page maintained by Martin Bland.

Last updated: 8 August, 2006.