2D Half-Normal Probability Plots

This type of graph is used to evaluate the normality of the distribution of a variable, that is, whether and to what extent the distribution of the variable follows the normal distribution. The selected variable will be plotted in a scatterplot against the values "expected from the normal distribution." The half-normal probability plot is constructed in the same way as the standard normal probability plot, except that only the positive half of the normal curve is considered. Consequently, only positive normal values will be plotted on the Y-axis.

Half-normal probability plots in STATISTICA. Note that in general half-normal probability plots, STATISTICA will not transform the input data (to be plotted) in any way. Hence, if your datafile contains, for example, prediction residuals from a regression analysis, and those residuals follow the normal distribution, then the half-normal plot will not provide a straight-line fit to those data unless you first transform the input data by computing their absolute values (x=abs(x)). However, in the plots of residuals that are provided as part of the statistical analysis modules, the absolute values of the residuals will automatically be plotted (i.e., the residuals are automatically transformed before the plot is constructed).

See also, Normal Probability Plots, Graphs - Normal Probability Plots, Graphs -Quantile-Quantile Plots, and Graphs - Probability-Probability Plots