Asking and Answering Questions about Line Plots and Bar Graphs
Students will be able to apply their knowledge of bar graphs and line plots to ask and answer interpretive questions about data.
- Tell students that artists have to make lots of decisions when they create a piece of art. They need to select colors, determine the size of objects, figure out how to shape images, and make many other choices. This is because they are creating a visual image that is going to communicate something to the viewer without using words. Explain that when data scientists create graphs, they too need to make decisions because they are creating a work that communicates something through a visual image.
- Project a bar graph for the class to see, or direct their attention to one in a resource that all students have. Ask students to discuss what decisions the creator of the graph had to make with a neighbour. Share ideas as a class.
- Examples: How wide to make the bars, what numbers to use on the scale, the colors/patterns on the bars, etc.
Explicit Instruction/Teacher modeling(15 minutes)
- Ask students to think about how much soda or other sugary drinks they consume per week. Using cans as the unit, have each student generate a number that is a close estimate. You may have to help them think about how many cans would equal a bottle.
- Create a Line plotOn the board, projector, or chart paper using this data.
- Determine the minimum and maximum, draw a horizontal line and add numbers (starting with the minimum and working up to the maximum), and add a title and labels.
- Calling on groups or rows, instruct students to come and add an X above their estimated number.
- Remind them that this strategy of organizing data is called a line plot. Discuss the line plot, prompting with interpretive questions like: "What are some conclusions/statements we can make about how much soda our class drinks?" "Who might be interested in this data? (Doctors, soda marketing companies, dentists, etc.)"
Guided practise(15 minutes)
- Consider how this same data might be translated into a bar graph. Keeping the line plot (don’t erase it), together create a bar graph using the data and discuss how the numbers across the horizontal axis could be configured as categories (ex. 0-2 = 1st bar, 3-5 = 2nd bar, etc.). Remind students that these are decisions that impact what the graph looks like and how information will be interpreted. Add a title and labels.
- Explain that you are now going to ask some questions about the graphs. You are going to discuss them and then they are going to write some questions.
- Which graph do you think better illustrates the sugary drinking habits of the class? Why?
- Is there another way you can think to display this data?
- What would happen if the bars represented individual numbers? How would that change the graph? What if the bars were bigger ranges, like one to 10 cans for one bar?
Independent working time(10 minutes)
- Ask students to work with a partner and write three word problems, each one on a different slip of paper: One about the line plot, one about the bar graph, and one comparing the two. Have them write 'Line,' 'Plot,' 'Bar Graph,' and 'Both' at the top of each.
- Collect the questions in a container.
Support: Offer sentence frames like, “How many people drink more than ____ cans per week?”
- Enrichment: Provide more complex graphs (found easily on the Internet) and have them create a word problem worksheet that requires interpretation of the graphs.
- Using equity sticks or another random method, call on students to come to the front of the class, draw a question, and answer it using the graphs. If a questions is unclear, select another one.
Review and closing(5 minutes)
- Revisit the idea of the artist and how the decisions are similar -- they both must consider the “message” they need to illustrate and make decisions to create a visual.