To assess prior knowledge, display a bar graph from a book or a newspaper, or one that you have made at the Bar Grapher Tool.
Ask students to tell how many data points are represented in each category.
Ask each student to write his or her first name on index cards, and then write on the card the number of vowels in the name. Ask students to group themselves according to whether they had one, two, three, or four vowels in their first name. If you have students with more than four vowels in their first name, add this choice as well.
Write the numbers 1, 2, 3, and 4 vertically on the board. (Allow enough space for index cards.) Ask students in each group to tape their index cards end to end in a line after the number that tells how many vowels are in their first name.
| Sample Names |
| Valerie Bertinelli | Paul Newman |
| Nicholas Cage | Jack Nicholson |
| Michael Caine | Christopher Reeve |
| Katherine Hepburn | Diana Rigg |
| Anthony Hopkins | Susan Sarandon |
| Meryl Streep | Ben Kingsley |
Record on the board how many students are in each group. Elicit from them a possible name for the bar graph.
| Vowels in Our First Names |
| 1 | Ben | Jack | Meryl | |
| 2 | Anthony | Paul | Susan | |
| 3 | Diana | Christopher | Michael | Nicholas |
| 4 | Valerie | Katherine | | |
Ask students to copy the bar graph on the Grid Paper. Circulate as students work to be sure that all students can successfully complete a bar graph.
Ask students what they can tell about the data from looking at the bar graph.
After students have offered several statements, encourage them to use numbers to compare the rows of the bar graph. Lead students to notice which number had the longest bar and which had the shortest bar. Inform them that the value that had the longest bar is called the mode. If two numbers occur more than the others, the data set is called bimodal.
Tell them that this is one of three measures of central tendency. Ask them to compute the range by subtracting the lowest number from the highest number (in the example, 4 - 1). Identify this as a measure of spread.
Next, open the Create a Graph and select the Bar Graph option. Clear the bar graph, and then ask volunteers to enter the class data into the recording section.
Call on students to type in a name for the bar graph, the values they will be bar graphing (1 - 4), and the number associated with each value. Ask volunteers to choose the colors of bars that they would like in the bar graph.
Next, select a student to choose "Horizontal” and the size you wish. Click “Create Printable Graph.” After students have discussed the bar graph, print out the bar graph for future reference.
Note that you can generate either a vertical or a horizontal bar graph with this software.
Return to the data entry page and choose the “Vertical” notation. Ask students to look at each of the orientations and compare them. Lead them to notice that changing the orientation does not affect the data.
Ask students to copy, label, and date the bar graph showing the length of the first names in the class. They should record their graphs on grid paper. Ask them to label and record the mode and the range of that data set.
Alternatively, you may create vertical bar graphs using the NCTM Bar Grapher Tool.
