1. Double Bar Graphs (Comparative Bar Graphs)

2. Primary & Secondary Data Primary Data: –Information that is collected directly or first hand –Example: Data collected by you through a survey Secondary Data: –Information that is not collected first-hand –Example: Data from a newspaper or Census At School (Canadian Statistics)

3. Discovery Activity With your partner, complete the “Discovery Activity” in the handout. –Orally discuss the answers to questions 1-3 –Write your answers to question 4

4. Discovery Activity – Bar Graphs

5. Discovery Activity – Questions to Consider 1.List 3 things these graphs tell you. 2.A) Approximately what percent of 13-year-old males spend no time exercising vigorously outside of school? B) Approximately what percent of 13-year-old males spend 7h or more exercising vigorously outside of school? C) What is the most common amount of time spent exercising vigorously by 13-year-old males? 3.Repeat question 2 for 13-year-old females. 4.A) Compare the two bar graphs. What differences can you see between males and females regarding exercise habits? Justify your observations. B) How could you make it easier to compare the two sets of data? Describe your ideas.

6. Easier to use a double bar graph?

7. 50 students in a junior high school were surveyed to find what their preferred mode of transportation is. Girls Mode of TransportationNumber Bicycle15 Skateboard6 Walking9 Boys Mode of TransportationNumber Bicycle9 Skateboard8 Walking3 Draw a double bar graph to show and compare the data in percent. Calculating & Graphing Percents: Example

8. Calculating Percents The total number of girls surveyed is 15 + 6 + 9 = 30 Girls Mode of Transportation NumberFractionDecimalPercent Bicycle1515/3015 ÷ 30 = 0.50.50 x 100% = 50% Skateboard66/306 ÷ 30 = 0.20.2 x 100% = 20% Walking99/309 ÷ 30 = 0.30.3 x 100% = 30%

9. Calculating Percents The total number of boys surveyed is 9 + 8 + 3 = 20 Boys Mode of Transportation NumberFractionDecimalPercent Bicycle99/209 ÷ 20 = 0.450.45 x 100% = 45% Skateboard88/208 ÷ 20 = 0.40.4 x 100% = 40% Walking33/203 ÷ 20 = 0.150.15 x 100% = 15%

10. One reason to graph using percents is you can compare groups of data that have different sizes (e.g., girls – 30; boys – 20). Graphing Percents

11. Features you need for a double bar graph: Different colours for the bars Connect the bars in each category, with a space between each category Add a legend Features of a regular bar graph (titles, intervals etc.)

12. Key Ideas A double bar graph shows how two or more groups of data compare. You can compare groups of data that have different sizes by using percents.