Activity 5: Scattergraph Exercise (80-100 minutes)

Students create a simple scattergraph to see the correlation between two variables.

Students will:

demonstrate an understanding of the correlation between population characteristics;
analyze, synthesize, and evaluate data;
construct a variety of graphs, charts, diagrams, and models to organize information.

peer assessment, directed by teacher, of the graph and the analysis using the criterion-referenced assessment outline created in Activity 4
formative assessment by teacher of the three analysis statements from each group

Model the creation of one scattergraph using an overhead and acetate sheet using data in Life Expectancy and Infant Mortality Statistics for Some Countries, Appendix 5.1. Use it to review the required components of an effective graph from Activity 4. The major criteria are in italics on the sample graph in Teacher’s Model of a scattergraph, Appendix 5.2.
Draw a line of best fit. The line should follow the trend of the dots. It is not necessary for the line to be absolutely accurate but it should follow the overall pattern of the dots.
As a class, students analyze the graph.

· Do the dots form a clear pattern? If a pattern is visible on the graph the data set selected shows some relationship

· Is there a steep or a gentle slope? This shows a relationship between the two variables: as one changes the other changes rapidly or slowly.

· Does it have a positive or negative slope? As one variable increases, does the other increase or does it decrease?

· Are all the dots close to the line you drew? Dots close to the line of best fit show a strong correlation. Scattered dots show a weak correlation.

· Model a concluding statement built around answering each of these questions.

Each student creates one scattergraph to show the relationship between literacy and birth rate for selected countries using data in Birth Rate and Literacy Rate for Some Countries, Appendix 5.3. A sample student graph is provided in Student Scattergraph, Appendix 5.4.
Each student researches to find the data on literacy and birth rate for their country and adds a labeled dot to represent their country on their finished scattergraph from Strategy 4 for their scrapbook.

If the class has access to computers, this exercise can be easily completed using a spreadsheet, graphing or drawing application.
Some students might explain why using numbers of people or area as one variable seldom produces a valid correlation.