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WHAT IS A STATISTICAL POSTER?

DEFINITION AND PURPOSE

There are many excellent references on the basics of developing a good data-based graphic. An annotated list is provided in the last section. This article describes a few basic guidelines for constructing a statistical poster.

A statistical poster is a display containing two or more related graphics (plots, charts, maps, etc.) that summarize a set of data, that look at the data from different points of view, and that answer some specific questions about the data.

Tukey (Statistical Science, 1990, Vol. 5, No. 3, 327-339) states that "Much of what we want to know about the world is naturally expressed as phenomena, as potentially interesting things that can be described in nonnumerical words." We collect data to describe and answer questions about phenomena. We present data to communicate our ideas to others. The purpose of a statistical poster, then, is to visually tell a story, from the data, about some phenomena, revealing to the viewer the conclusions that can be drawn.

A poster has one major disadvantage, however. Since there is no narrator to tell the story, nor an accompanying report to discuss the data, the poster must be able to stand alone; it should not have to be explained. For this reason, special care must be taken to present ideas clearly. Not only must the viewers understand the individual graphics, but they must also understand the relationships among the graphics, and how the graphics address the question(s) being studied.

DATA-BASED PROBLEM SOLVING

Data are everywhere. Teachers may assist students by suggesting topics of interest, but students should have little trouble generating or collecting data, about themselves, about their schools, about their neighborhoods—about interesting phenomena in their world. The level of reasoning and the complexity of the problems will differ greatly with the maturity of the students; but even in the lower grades, formulating and solving problems based on data should be the primary focus. The poster, then, becomes a communications tool, a tool for the graphical presentation of their data.

In the higher grades, the poster can be used not only for data presentation, but also as a graphical problem-solving tool. Further, at its best, the poster should demonstrate that the scientific method of solving a problem has been used:

• Was there a carefully focused question or questions?
• Were appropriate data collected?
• Were the data analyzed intelligently?
• Were the correct conclusions drawn?

BASIC GUIDELINES

While constructing a poster, it is important to keep in mind that the central idea of the study should be the most prominent feature of the poster. To bring the main idea into focus, questions such as the following should be asked. "What is the purpose for displaying this information?" "What comparisons should be made?" "Which trends should be shown?" Questions should be asked until the central idea of the study becomes clear. This, then, becomes the focal point of the poster.

The poster must reveal what the data have to say. It must allow the viewer to see the data, that is, to see the variation in the data and to see the structure of the data—including the important patterns (or lack of a pattern) in the data, and the data points that do not fit the pattern. It must also show the conclusions that can be drawn from the data. Further, each graphic on the poster should convey new information about the data—a pattern or structure, for example, that cannot be seen in the other graphics.

The poster title should be informative to reduce the need for additional explanatory text. For example, the title can indicate the questions addressed by the graphics or can even convey the major conclusion to be drawn from the data.

Each graphic's legend should be positioned so that there is no question which graphic and which legend go together. Further, each graphic and its legend should stand alone. If the graphics need to be viewed in a certain order, however, then the viewer's eyes must be guided in the right sequence.

The poster should not contain trivial and extraneous information, linework, or lettering. In particular, redundancy in titles and legends should be omitted. Only explanations that are needed to make the conclusions clear and obvious should be included. Data tables should not be shown on the poster; reading off numbers is not the point of the display.

Colors that clash and those that blend should be avoided; a few harmonious colors that are easily visible should be chosen. The key to using colors effectively is restraint; the colors should not distract the viewer, but should enhance recognition of the structure of the data and of the conclusions.

Tufte (The Visual Display of Quantitative Information, 1983, 13) stated that graphics may "...reveal the data at several levels of detail, from a broad overview to the fine structure." In a similar sense, a poster may do the same. At a distance, perhaps only a broad overview of the poster and the data is possible; main titles are visible and overall outlines of the data as revealed by the graphics can be seen. On closer inspection, however, aspects such as individual data labels and legends can be seen more clearly.

A FINAL NOTE

The NCTM Standards for Curriculum and Evaluation in School Mathematics, released in 1989, present the vision that problem solving is tile main goal of mathematics instruction at all levels, and call for student involvement in statistical activities at all grade levels. They indicate that statistical thinking should start in the primary grades with the creation of student data from class activities and surveys on topics of student interest. In higher grades, the emphasis is on collecting, organizing, summarizing, and interpreting data from other school disciplines such as the physical or the social sciences, as well as outside interests of the students. Graphical displays are exceptionally powerful tools for data presentation and for data analysis.

John Schollenberger
Cleveland Chapter, ASA
Updated 10/96

REFERENCES ON GRAPHICS

• Cleveland, W. S. (1985). The Elements of Graphing Data; Hobart: Summit, NJ.
• Cleveland, W. S. (1993). Visualizing Data; Hobart: Summit, NJ.
• Circio, F. R. (1989). Developing Graph Comprehension, elementary and middle School activities; The National Council of Teachers of Mathematics: Reston, VA.
• Huff, D. (1954). How to Lie With Statistics; W. W. Norton: New York, NY.
• Jones, G. E., (1995). How to Lie with Charts; SYBEX: San Francisco, CA.
• Landwehr, J. M. and Watkins, A. E. (1987). Exploring Data, a unit of the Quantitative Literacy series; Dale Seymour: Palo Alto, CA.
• Russell, S. J., and Corwin, R. B. (1989). Statistics: The Shape of the Data, a unit of study for grades 4–6 from Used Numbers: Real Data in the Classroom; Dale Seymour: Palo Alto, CA.
• Russell, S. J., et al. (1995). The Shape of the Data, a unit of the Investigations in Number, Data, and Space curriculum for grades 4–5; Dale Seymour: Palo Alto, CA.
• Tufte, E. R. (1983). The Visual Display of Quantitative Information; Graphics Press: Cheshire, CT.
• Tufte, E. R. (1990). Envisioning Information; Graphics Press: Cheshire, CT.
• Wainer, H. (May, 1984). "How to Display Data Badly," The American Statistician, 38, No. 2; pp 137-147.
• Wainer, H. and Thissen, D. (Winter, 1988). "Plotting in the Modern World: Statistics Packages and Good Graphics," Chance, 1, No. 1; pp 10-20.
• Wallgren, A., et al. (1996). Graphing Statistics & Data; SAGE Publications: Newbury Park, CA.