local focus and more accurate horizontal scanning. The grouping in units of five is a compromise, being more than the suggested perceptual groups of four. However, thinking about years in units of 10 is convenient and use of groups of 5 is compatible with this.

AVAILABLE TOOLS

Carr added that interactive tables have a history and a future. Historically, Table Lens software has provided many interactive features (see Rao and Card, 1994). Now, variable selection, row and column reordering, and focusing tools are increasingly common, and statistical methods are more available to support the making of comparisons in a table context.

Although tables remain important for some tasks, there are merits to using statistical graphics for many discovery, analysis, and communication tasks. Carr showed a linked micromap that uses a graphical user interface for variable selection and uses statistical graphics to represent estimates and confidence intervals for both the primary variable of interest and related variables.2 The graphics include reference values and color-linked micromaps that show spatial patterns. The interactive applet provides “drill-down” capabilities from states to counties, and supports reordering rows and columns.

The website for the Nation’s Report Card3 provides instructive example tables related to state achievement (student averages) on standardized tests. These tables foster statistical comparisons in two ways. First, the variables available for interactive selection include differences, such as differences between male and female average scores for each state. The 95 percent confidence intervals of such differences for each state can draw attention to states whose intervals do not include zero. Such differences are unlikely to be due to random variation and so are of interest in investigating disparities.

Second, the interactive table on the National Center for Education Statistics website supports selection of a reference value to use in making comparisons. For example, selecting the national public value adds a table column that shows states in one of three categories: those with confidence intervals below, including, or above the national public reference value. People find it easy to think in terms of three ordered categories, such as small, medium, and large, and so they also find it easy to think of states as belonging to one of three categories. This column of state categories can be

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2 The example shown at the workshop is available at: http://statecancerprofiles.cancer.gov/ micromaps, a database maintained by the National Cancer Institute.

3 This website of the National Center for Education Statistics is available at: http://nces.ed.gov/nationsreportcard/states [January 2013].



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