## The Tale of Scale

### Michelle GowanLiberty County Schools

#### Description

Students produce three bar graphs using a range of data for various scales along the y-axis.

#### Objectives

The student interprets and applies various scales including those based on number lines, graphs, models, and maps. (Scale may include rational numbers.)

#### Materials

-Overhead projector, transparency, and marking pens
-Transparency of teacher class totals (see #1 of teacher preparation)
- One ruler per student
-Three sheets of graph paper or plain paper for each student
-Statistical data for student graphing activity (see attached file)

#### Preparations

1. Prior to the class meeting, teacher produces a bar graph on transparency film using the following information:
y axis = every line is 1/2 inch apart and labeled in 10's from 0-100. The title is The Number of Students in Each of Mr./Mrs. Teacher's Classes. The teacher draws a bar for 1st Period to equal 30, 2nd Period to equal 21, 3rd Period to equal 28, 4th period to equal 0, 5th period to equal 35, and 6th Period to equal 24. Colored markers might be used to set off each class period.

2. Gather materials.

3. Prepare handouts.

#### Procedures

1.To gain students' attention, the teacher will ask students to assist with determining the total number of students in each of his/her classes (the teacher's classes) by reading the bar graph. (This bar graph data is located in the preparation section.) Display the bar graph and use it to demonstrate the importance of selecting the appropriate scale. Students should be asked to interpret the total for each class period by reading the graph. The goal is that students will not be able to accurately determine the amounts. Use this as a teaching moment to stress why drawing graphs on a readable scale is important. While there is no rule of thumb on the intervals, students should make the data so that it can be read on one page and that each amount can be clearly determined. Usually, data scales should not be less than one place value above the largest number.

2. To confirm that students understand intervals, state various ranges of numbers and call on students to suggest appropriate graphing intervals. For example, if the amounts to be graphed ranged from 0-2000 and the data was 200, 900, and 1500, the ideal interval might be 200.

3. Provide for practice by providing students with graphing paper, a ruler, and data located in the attached file and direct students to complete their own bar graphs using a y-axis scale no larger than one place value from the largest number of the data. Emphasize the need to be able to determine numbers that don't exactly match those on the y-axis.

#### Assessments

Students complete three bar graphs, each with a scale for the y-axis that is no greater than one place value higher than the largest number.

#### Attached Files

Data for the graph activities is included.     File Extension: pdf