Plot: Box/Whisker

The options described here are used to define the statistics that are indicated by the components of each box-whisker combination in box and whisker type plots, as well as some of the characteristics of the plotted box/whiskers. The method of categorization for categorized box and whisker plots can also be specified on this tab. These options are available in the Box/Whisker dialog as well as in the Graph Options dialog - Plot: Box/Whisker options pane.

Plot. Use the Plot drop-down box to select the plot to which you want to make changes. If you have several plots in one graph, you can assign names to each plot using the Name field on the Plot: General tab.

Statistics. Click the Statistics button to display the Statistics dialog for box-whisker type plots, in which you can select a variety of statistics that will be included in your graph. You can select the nonparametric Kruskal-Wallis test (see also Nonparametric Statistics) and the ANOVA F test (see, for example, General ANOVA/MANOVA). Note that if you do select statistic(s) to include in your graph, the Add Legend dialog will also be displayed, which is used to select where and how to attach the statistic(s) to the graph. Statistics will not be calculated for graphs that do not involve categorization within variables (e.g., for box and box and whisker plots for multiple variables without categorization, or plots from blocks of data).

Type. The Type group contains options to further define the plot.

Middle point. Use the Middle point drop-down box to select the statistic Mean or Median to be used to determine the center (middle) points in the plot (variable and group). Note that the specific method used to compute the Medians (and percentiles) can be configured for all functions and statistical analyses in the Options dialog - Analyses/Graphs: Limits options pane (accessible by selecting Options from the Tools menu). For more information, see Percentile Calculation Options in STATISTICA.

Pooled Variance. The setting of the Pooled Variance check box determines how the standard deviations and standard errors (for the means) are computed from grouped data. When the Pooled Variance check box is selected, STATISTICA computes the pooled within-group (category) variance for all groups (categories), and uses this value as an estimate of σ (Sigma) in computing the standard errors for the means. For more details on this option see the description of the Pooled Variance check box on the Means with Error Plots - Advanced tab. Note that this check box is only available when you select Mean as the Middle point.

More. Click the More button to display the Box/Whiskers More Options dialog, in which you can select additional options to compute the box and whiskers, control the display of outliers and extremes, and use the trimmed distribution of the dependent variable to compute mean/median. This option is not available when the Scatterplot with error bars check box is selected.

Box value. Use the Box value drop-down box to assign a statistic to the box drawn in the box and whisker plot. The options available depend on the Middle point you selected. For the Median, you can select Percentiles, Min-Max, and Constant (draw a box to enclose a fixed-value interval around the middle point); for the Mean Middle point, you can select Std. Dev. (standard deviation), Std. Err. (standard error of the mean), Conf. Interval (confidence interval for the mean), Min-Max (minimum and maximum value of the dependent variable), and Constant. For additional specifications (e.g., to set the specific percentiles, percent value for the confidence intervals, constant, etc.) click the More button to display the Box/Whiskers More Options dialog. The specific method used to compute the percentiles can be configured for all functions and statistical analyses in the Options dialog - Analyses/Graphs: Limits options pane. For more information, see Percentile Calculation Options in STATISTICA.

Whisker value. Use the Whisker value drop-down box to choose how the ranges of Whiskers are computed; the options available in this box depend on the Middle point you selected. For the Median middle point, the available choices include Percentiles, Non-outlier range (see Outliers), Min-Max (minimum and maximum values), and Constant (draw the whiskers to enclose a fixed-value interval around the middle point). For the Mean middle point, available options are Std. Dev. (standard deviation), Std. Err. (standard error of the mean), Conf. Interval (confidence interval for the mean), Non-outlier range (see Outliers), Min-Max (minimum and maximum value), and Constant. For additional specifications (e.g., to set the specific percentiles, percent value for the confidence interval, constant, etc.) click the More button to display the Box/Whiskers More Options dialog. The specific method used to compute the percentiles can be configured for all functions and statistical analyses in the Options dialog - Analyses/Graphs: Limits options pane. For more information, see Percentile Calculation Options in STATISTICA.

Scatterplot with error bars. Select this check box to specify that, when the OK button is clicked, error bars will be generated in the plot for all x-axis values that have more than one y-value associated with them. Note that when this check box is selected, the More option, the options in the Intervals group, the Intervals value format option, and the Scale X option become unavailable.

Intervals. Use the options in the Intervals group to select a method (Integer mode, Unique values, Categories, Boundaries, Codes, or Multiple subsets) to define the manner in which the values in the chosen grouping variable will be used to determine the categories for the graph. Note that separate means (medians, etc., as specified on this tab) will be computed for each group as defined by the values in the grouping variable. The methods for categorizing the values in the grouping variable are discussed in detail in Methods of Categorization.

Change Variable/Specify Boundaries/Specify Codes/Specify Subsets. Note that the name of this button changes depending on the Interval option button that is selected. Click the Change Variable button to display a standard variable selection dialog, which is used to change the selection of the grouping variable to which the Intervals options apply. Click the Specify Boundaries/Codes/Subsets button to display various dialogs in which you enter the boundaries, codes, or subsets that are used to create user-defined categories.

Properties. The options in the Properties group are used to specify various aspects (sizes, etc.) of the components of the box/whiskers.

Intervals value format. Click the Intervals value format button to display the Value Format dialog; the display format chosen in that dialog will be used to label the horizontal (by default) axis in the plot, along which multiple box/whiskers are plotted. See also the Intervals group for the different ways in which the data can be categorized.

Width: Box, Whisker. The options in the Width group box are used to determine the widths of the Box(s) and Whisker(s) in the plot, relative to the scaling (step size) for the horizontal axis, i.e., the axis along which multiple box/whiskers for multiple groups or variables are plotted. If you specify 100% as the width in either the Box or Whisker field, then the respective graph component will be as wide as a single "step" along the horizontal x-axis; so if multiple boxes and whiskers are plotted, they most likely will run into each other. Thus, specify (typically) less than 100%.

Scale X. From the drop-down list, you can select Logical or Coordinate. Logical scaling is primarily used for categorical x-axis values. Coordinate scaling is used for continuous x-axis values when a grouping variable is selected; this allows application of user-defined boundaries.