Students will be able to
● use ratio language to describe the relationship between quantities as part to part or part to whole
● compare decimals, percentages, ratios, and fractions to describe a statistic
● create bar graphs using information collected from infographics containing real-world data
Common Core State Standards: 6.RP.A.1, 6.RP.A.2, 6.RP.A.3, 6.SP.A.1
Vocabulary: Body mass index (BMI), ratio, obesity, infographic, fraction, decimal, percentage
Materials: Per group of two to three students: digital graphing program or materials for creating graphs (paper, colored pencils, rulers, etc.)
1. Introduction (5 minutes, whole group)
Ask students if they know what body mass index, or BMI, is. Explain that BMI is a ratio of height to weight and correlates with health outcomes such as heart disease, diabetes, cancer, and overall mortality. The formula used to calculate BMI is: weight (kg)/[height (m)]2. Using pounds and inches, the formula is: weight (lb)/[height (in)] 2 x 703.
Next, discuss the meaning of obesity. Highlight the following ranges of BMI, as defined by medical professionals: 18.5 to 24.9 is considered healthy, 25.0 to 29.9 is considered overweight, and 30 or higher is classified as obese.
2. Data in Different Forms (10 minutes, whole group)
Explain to students that an infographic, or information graphic, is a visual image designed to present complex information quickly and clearly. Present the infographics to students. Give them a minute or two to make some observations. Then, ask, How does the use of these graphs powerfully present the changes in obesity rates in the U.S.?
Next, have students analyze both graphs—the circular graph and the pictograph—and ask, How could the data presented in the different graphs be expressed as ratios and fractions? Have students express the numbers as a ratio, fraction, decimal, and percentage for the year 1960 (1:140, 0.9%, 0.09, and 9/100). Discuss that while fractions can only be expressed as part to whole (i.e., 0.9% or 9/100), ratios can represent both part to whole and part to part. While we can state that 1 in 140 people were extremely obese, we can also state that extremely obese to obese was 1 to 19.
3. Graphing Obesity Trends (15 minutes, whole group)
Ask students to look at the infographics in groups and record the ratio, fraction, decimal, and percentage rates for one category (such as “Not overweight or obese” and “Obese”) over the five decades. Ask students, What can this information tell you? What are the benefits or challenges of recording the data as a ratio, fraction, decimal, or percentage? Which is easiest to interpret? Why? When is it best to use a ratio, fraction, decimal, or percentage? Why?
Next, have students convert the information that they have examined in the infographics into another type of graph, such as a bar graph, that either provides data for a given year or represents change over time. Have each group record five questions that the new graph could answer. Then, have teams of students swap graphs and answer the questions.
If time allows, encourage students to make comparisons of the strengths and weaknesses of each type of graph for this data. Discuss reasons why it may be better to use one graph over another.
4. Conclusion (5 minutes, whole group)
Review the data recorded and the strategies that students used for collecting information for and creating their graphs.
Activity Extension: Have students research the actual population data for years represented in the obesity infographics. What would the actual numbers be, for each year, of people who fit into the category? What other statistical information could help researchers understand what has contributed to the rise in obesity for the U.S. population?