Creating Box Plots with a Graphing Calculator

Today’s Learning Goal We will begin to understand how to create and interpret box plots with a graphing calculator.

Previously, we made a box-and-whisker plot for the data at the left using the five-number summary. BagBlue Box-and-Whisker What are the five numbers we need to create a box-and-whisker plot? Awesome…1) the minimum 2) the first quartile (Q 1 ) 3) the median (Q 2 ) 4) the third quartile (Q 3 ) 5) the maximum

Using the Graphing Calculator We can use our graphing calculators to make box plots for data also. To put data into your calculator, press the “STAT” button as we did before. STAT Now press “ENTER” to select the edit screen to put data in. Enter BagBlue

Using the Graphing Calculator If you have data in your lists, you can clear the list by putting the cursor over top of the L1 (or L2) at the top and pressing “CLEAR”. Now put the following blue M&M data down the L1 column. Clear Make sure you have 11 total data points for all 11 bags. BagBlue

Using the Graphing Calculator Now that you have the data in the calculator, press the “2 nd ” button and then the “Y=” button to access the statistical plot screen. Press “Enter” to enter the Stat-Plot screen. 2nd Y= Make your Stat-Plot screen match the one shown at the right by pressing “ENTER” with your cursor over each highlighted part. Enter BagBlue

Using the Graphing Calculator Press the “Window” button and make the x-values go from 0 to 25 by 5s and the y- values go from 0 to 5 by 1s. Press “Graph” to view the box plot of the data. Press the “Trace” Button and you will see some information pop up. Win Graph Trace BagBlue

Using the Graphing Calculator Notice that it tells you the median is 13 blue M&Ms at the bottom of the graph. If you press the right and/or left directional arrows, you can trace to the min, max, Q 1, and Q 3 values also! What is the third quartile for this data? BagBlue < Fantastic…Q 3 = 16!

Using the Graphing Calculator If we wanted to make more than one box plot, we can use our graphing calculators to do that also. Suppose we wanted to put the Red M&M data into our calculator. What button should we push to enter data? STAT Now press “ENTER” to select the edit screen to put data in. Enter BagRed Nice…”STAT”.

Using the Graphing Calculator Now put the following red M&M data down the L2 column. Make sure you have 11 total data points for all 11 bags. BagRed Now that you have the data in the calculator, press the “2nd” button and then the “Y=” button to access the statistical plot screen. 2nd Y= Notice Plot 1 is still On for the blue M&M data. Cursor down to Plot 2 and Press Enter. Enter

Using the Graphing Calculator Make sure your Plot2 screen looks like the one at the right. Be sure to tell the calculator that the red M&M data is coming from the L2 list by pressing the “2 nd ” and “2” buttons. Press “Graph” to see both box plots. BagRed nd 2 Graph What is wrong with our graph? We cannot see the maximum!

Using the Graphing Calculator What can we do to be able to see the maximum for the Red M&M data? Press “Window”. What should we change the x-max to so that we can see the entire box plot? Win BagRed Great…change the window. Good…anything more than the maximum red data point of 34.

Using the Graphing Calculator Let’s make the x-max be 40. Then, press “Graph” to see the box plots again. Again, you can press “Trace” to see the 5-number summary values. BagRed Graph If you press the cursor up/down buttons it will toggle between the two box plots. Trace <

Partner Work You have 30 minutes to work on the following questions with your partner.

For those that finish early Use your graphing calculator to make a box plot of the following data that shows the ages of forty drivers killed in car crashes using an interval size of , 76, 18, 81, 28, 29, 18, 18, 27, 20, 18, 17, 70, 87, 45, 32, 88, 20, 18, 28, 17, 51, 24, 37, 24, 21, 18, 18, 17, 40, 25, 16, 45, 31, 74, 38, 16, 30, 17, 34 According to the box plot, which age range seems to be the most likely to be killed by a car crash?

Big Ideas from Today’s Lesson Using a graphing calculator helps to minimize the time it takes to make a graph and it allows you to focus on its interpretation and meaning.

Homework Use your graphing calculator to make the box plots on the following pages of your textbook. Then, make a sketch of the box plot. Pgs. 620 – 621 (14, 15)