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# Primary Source Set Charts and Graphs

The resources in this primary source set are intended for classroom use. If your use will be beyond a single classroom, please review the copyright and fair use guidelines.

## Teacher’s Guide

To help your students analyze these primary sources, get a graphic organizer and guides: Analysis Tool and Guides

## Background

Human beings have represented numeric information for millennia, from the cuneiform of the ancient Sumerians to the Huexotzinco Codex of Mesoamerica to spreadsheets or tables of numbers in use today. But there is a difference between representing numbers and showing a summary view of the information using a chart or graph. Observing, reflecting on, and questioning charts and graphs allows students to hone their data literacy skills to better understand the information presented. These primary sources provide opportunities for students to connect the computational and mathematical thinking needed to interpret data with the historical subjects of these charts.

While methods for counting and representing numbers are as old as humankind, current methods for representing data are only about 200 years old. Philosopher Nicole Oresme represented some velocity and time relationships with drawings of pan-pipes in the 14th century, and Rene Descartes envisioned the rectangular coordinate system in 1637. But William Playfair is credited with creating a trend line on a grid system as well as bar and circle charts around the turn of the 19th century. Near the middle of that century, Florence Nightingale created another type of chart, known as a coxcomb graph or Nightingale rose diagram, to convince British authorities to pay more attention to sanitation in military hospitals. Graphs were used extensively in the Statistical Atlases of the United States published in the late 19th century. At the turn of the 20th century, W.E.B. Dubois created a set of charts documenting the experiences of Black Americans in Georgia for an exposition in Paris, using traditional and artistic graphs. Graphs and charts to represent data became a part of the school curriculum in the first half of the 20th century.

Data representations in primary sources have a purpose behind them, and often the purpose is more than simply providing information. Just like artists of political cartoons, the creator of a chart is calling attention to important ideas and often hiding other details in the process. Graphs also reflect the biases and norms of the period in which they were created. Analyzing charts and graph requires us to ask some of the same questions we would ask of any primary source: Who created it? For what purpose? What story does the chart tell? But we also ask questions more specific to this type of media: What is the scale, and is it consistent? What information appears most important and what might be hidden? What is the source of the data? How might the creator’s use of colors or shapes (like human figures for the bars on a chart) or other artistic or editorial flourishes affect the viewer’s emotional response and interpretation? And what was happening in the time period and place where the chart was created or viewed? Analyzing historic charts and graphs provides students both with practice using their math reasoning and data literacy skills and with additional context about periods and events in history.

## Suggestions for Teachers

As part of a math lesson, ask students to notice, think, and wonder about a graph showing a trend. Student responses can help teachers introduce important math topics such as maximum and minimum points, rates of change, and general graph reading skills. Student questions may also lead to further research on the topic of the graph.

Using a page from a historic newspaper containing a chart, ask students to discuss what information is represented in the chart and how it relates to the information in an accompanying article. Why did the editor choose to represent this particular information using a chart? How might a reader view the information from the article if the chart were not present, or if the information were represented on a different type of chart?

Present two related charts to the students. The items may contain similar information from two periods in history, or be two different representations of the same or related information. Ask the students to compare and contrast the charts: Do they represent the same data? If so, what information is highlighted and what is hidden in each? If they represent related data, what is the relationship? If the charts are of different types, why might the creators have made these choices? If the charts are the same type, are the scales similar? How might viewers respond to each chart? Next, look at the item records and discuss how differences in time or place may have influenced the charts’ creators.

Reveal a graph one piece at a time and ask students to conjecture about the purpose and information the graph might present. For example, show only the scale and title, and ask students to predict the shape and details of the graph. Ask them what evidence supports the prediction. Or, show the graph without the scale and with minimal contextual information and ask students to conjecture about what the graph represents. For each prediction or guess, ask the students to explain the reasoning that led them to those conclusions. Then, reveal only part of the missing material, and ask students how they might revise their thinking. After showing the complete image, discuss how the students’ perspectives changed as the image was revealed.