PLOT Subcommand (EXAMINE command)

PLOT controls plot output. The default is a vertical boxplot and a stem-and-leaf plot for each dependent variable for each cell in the model.

  • Spread-versus-level plots can be produced only if there is at least one factor variable on the VARIABLES subcommand. If you request a spread-versus-level plot and there are no factor variables, the program issues a warning and no spread-versus-level plot is produced.
  • If you specify the PLOT subcommand, only those plots explicitly requested are produced.

BOXPLOT. Vertical boxplot. The boundaries of the box are Tukey’s hinges. The median is identified by a line inside the box. The length of the box is the interquartile range (IQR) computed from Tukey’s hinges. Values more than three IQR’s from the end of a box are labeled as extreme, denoted with an asterisk (*). Values more than 1.5 IQR’s but less than 3 IQR’s from the end of the box are labeled as outliers (o).

STEMLEAF. Stem-and-leaf plot. In a stem-and-leaf plot, each observed value is divided into two components—leading digits (stem) and trailing digits (leaf).

HISTOGRAM. Histogram.

SPREADLEVEL(n). Spread-versus-level plot with the Test of Homogeneity of Variance table. If the keyword appears alone, the natural logs of the interquartile ranges are plotted against the natural logs of the medians for all cells. If a power for transforming the data (n) is given, the IQR and median of the transformed data are plotted. If 0 is specified for n, a natural log transformation of the data is done. The slope of the regression line and Levene tests for homogeneity of variance are also displayed. The Levene tests are based on the original data if no transformation is specified and on the transformed data if a transformation is requested.

NPPLOT. Normal and detrended Q-Q plots with the Tests of Normality table presenting Shapiro-Wilk’s statistic and a Kolmogorov-Smirnov statistic with a Lilliefors significance level for testing normality. If non-integer weights are specified, the Shapiro-Wilk’s statistic is calculated when the weighted sample size lies between 3 and 50. For no weights or integer weights, the statistic is calculated when the weighted sample size lies between 3 and 5,000.

ALL. All available plots.

NONE. No plots.

Example

EXAMINE VARIABLES=CYCLE BY TREATMNT /PLOT=NPPLOT.
  • PLOT produces normal and detrended Q-Q plots for each value of TREATMNT and a Tests of Normality table.

Example

EXAMINE VARIABLES=CYCLE BY TREATMNT /PLOT=SPREADLEVEL(.5).
  • PLOT produces a spread-versus-level plot of the medians and interquartile ranges of the square root of CYCLE. Each point on the plot represents one of the TREATMNT groups.
  • A Test of Homogeneity of Variance table displays Levene statistics.

Example

EXAMINE VARIABLES=CYCLE BY TREATMNT /PLOT=SPREADLEVEL(0).
  • PLOT generates a spread-versus-level plot of the medians and interquartile ranges of the natural logs of CYCLE for each TREATMENT group.
  • A Test of Homogeneity of Variance table displays Levene statistics.

Example

EXAMINE VARIABLES=CYCLE BY TREATMNT /PLOT=SPREADLEVEL.
  • PLOT generates a spread-versus-level plot of the natural logs of the medians and interquartile ranges of CYCLE for each TREATMNT group.
  • A Test of Homogeneity of Variance table displays Levene statistics.