Introduction to Box Plots
Lesson 14 of 22
Objective: SWBAT: • Identify and label the minimum, maximum, lower quartile, upper quartile, and mean of a data set and box plot. • Analyze and compare box plots.
See my Do Now in my Strategy folder that explains my beginning of class routines.
Often, I create do nows that have problems that connect to the task that students will be working on that day. Today I want students to analyze a circle graph in order to answer questions. Each edition of Scholastic Action typically includes a graph on its back page.
I ask for students to share their thinking. Students are engaging in MP3: Construct viable arguments and critique the reasoning of others.
I introduce the problem to students. I want students to apply what they already know minimum, maximum, and median to analyze the box plot. Students participate in a Think Write Pair Share. I walk around and monitor student progress as they work.
I call on students to share out their ideas. I push students to support their idea with data from the set. I am interested to see what students think about the dots at 28 and 39. Students are engaged in MP3: Construct viable arguments and critique the reasoning of others and MP2: Reason abstractly and quantitatively.
I reveal the name and definition of each part of the box plot. I show students that finding the lower quartile and upper quartile is just finding the median of a different part of the data set. I want students to see the connection between how each part is identified in the data set and then translated to the box plot.
Percent of Data
I have students participate in a Think Write Pair Share. Students are engaging in MP3: Construct viable arguments and critique the reasoning of others. I want students to make a connection between what they know about the median and the percent of data. If students understand that a median splits the data set down the middle, they should understand that 50% of the data is before the median and 50% of the data is after the median. Students can use the same reasoning to determine that 25% of the data is between the minimum and the lower quartile.
I call on students to share out their observations. If students are struggling, I may ask one or more of the following questions:
- How fraction of the data is before the median? After?
- How can we express that as a percent?
- What does the upper quartile represent?
- What percent must be after the upper quartile?
I want students to share out what they think the word quartile means. If students are struggling, I write these words on the board: quart, quarter, and quartet. I ask students to think about what the word part “quart” means in each word. I want students to see that quart- connects to four. There are four quarts in a gallon, four quarters in a dollar, and four people in a quartet. If we break our data into quartiles, we are breaking it up into four parts. This means that each quartile represents ¼ or 25% of the data in the data set.
Analyzing Box Plots
- Before this lesson I create and Post a Key.
I explain to students that they will be working to analyze the box plots. I ask students what they can do if they get stuck. I want students to realize that they can check their notes and check in with their partner if they are stuck, before asking me a question.
As students work, I walk around and monitor student progress and behavior. If students complete a page, I quickly scan their work. If they are on track, I send them to check their work with the key. If students are struggling, I may ask them one of the following questions:
- What is the question asking?
- What is does this part of the box plot tell us? Where can we find it?
- What did our notes say?
- What does a quartile represent?
If students complete the questions they can work on the challenge problems.
Closure and Ticket to Go
I ask students to flip to the closure problem. I ask students how the age of the players on the Houston Rockets compares to the age of the players on the Chicago Bulls. I explain that they need to write 5 observations by analyzing the box plots. They can use the questions at the bottom to help them if they are stuck.
Students participate in a Think Pair Share. Students are engaging in MP1: Make sense of problems and persevere in solving them and MP3: Construct a viable argument and critique the reasoning of others.
I call on students to share out their observations. I push students to use accurate language and to use the box plot to support their observation. Students are engaging in MP6: Attend to precision.
I pass out the Ticket to Go and the Homework.