Choose a Scale
10 min
Narrative
The purpose of this Warm-up is to elicit the idea that adjusting the scale changes the size of the bars in a bar graph and can make it easier or more difficult to interpret. While students may notice and wonder many things about these graphs, the different scales in the bar graphs are the most important discussion points.
Launch
- Groups of 2
- Display the graphs.
- “What do you notice? What do you wonder?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Share and record responses.
Student Task
What do you notice? What do you wonder?
Sample Response
Students may notice:
- The data is the same.
- The jumps on the scales are different. The highest number on the graphs is different.
- It’s harder to tell the number for guinea pigs on the last graph.
Students may wonder:
- Why are the jumps on the scales different?
- Why are the lines the same on each graph?
Synthesis
- “How are the three graphs different?” (They show the same data, but the bars are different heights. They have different scales.)
Standards
Building Toward
- 3.MD.3·Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. <em>For example, draw a bar graph in which each square in the bar graph might represent 5 pets.</em>
- 3.MD.B.3·Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step “how many more” and “how many less” problems using information presented in scaled bar graphs. <span>For example, draw a bar graph in which each square in the bar graph might represent 5 pets.</span>