Chapter 1 Section 3. Page 22. A graph is a visual display of information or data. There are three types of graphs.

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1 Chapter 1 Section 3 Page 22 A graph is a visual display of information or data. There are three types of graphs. Graphs are pictures that help us understand amounts. These amounts are called data. There are many kinds of graphs, each having special parts. Graphs are useful for displaying numerical information in business, science, sports, advertising and many everyday situations. All graphs are used to display data. All three graphs are used to display data. A line graph shows relationships between two variables. A bar graph can be used to compare information. A circle graph can be used to show percentages. A circle graph, or pie graph, is used to show how some fixed quantity is broken down into parts. The slices represent the parts and usually are represented as percentages of total. A circle graph is shaped like a circle. It is divided into fractions that look like pieces of pie, so sometimes a circle graph is called a pie graph. Many times the fractional parts are different colors and a key explains the colors.

2 A bar graph uses bars to show data. The bars can be vertical (up and down), or horizontal (across). The data can be in words or numbers. A bar graph is useful for comparing information collected by counting. Each bar represents a quantity counted at a particular time which should be stated on the graph. The independent variable is plotted on the X-axis and the dependent variable is plotted on the Y-axis. What is the IV on this graph and what is the DV on this graph? A line graph shows points plotted on a graph. The points are then connected to form a line. The points are connected because they are related. A line graph can show any relationship where the DV changes due to a change in the IV. Line graphs often show how a relationship between variable changes over time.

3 Independent Variable: An independent variable is the variable you have control over, what you can choose and manipulate. It is usually what you think will affect the dependent variable. In some cases, you may not be able to manipulate the independent variable. It may be something that is already there and is fixed, something you would like to evaluate with respect to how it affects something else, the dependent variable like color, kind, time. Example: You are interested in how stress affects heart rate in humans. Your independent variable would be the stress and the dependent variable would be the heart rate. You can directly manipulate stress levels in your human subjects and measure how those stress levels change heart rate. Dependent Variable: What you measure in the experiment and what is affected during the experiment. The dependent variable responds to the independent variable. It is called dependent because it "depends" on the independent variable. In a scientific experiment, you cannot have a dependent variable without an independent variable.

4 Example: You are interested in how stress affects heart rate in humans. Your independent variable would be the stress and the dependent variable would be the heart rate. You can directly manipulate stress levels in your human subjects and measure how those stress levels change heart rate. Graphs are a visual representation of data. Scientists often graph their data to detect patterns The type of graph used is based on the conclusion you want to identify. Line graphs show how a relationship between two variables changes over time. Bar graphs are best used to compare information collected by counting. Circle graphs show how a fixed quantity is broken down into parts.

5 Class assignment Class survey of the month in which each student s birthday occurs and tallies these data on the board. Students record this information on a sheet of paper. Each student makes both a bar graph and a circle graph to show the information.

6 Review Graphs Name: 1. Identify the kind of graph that would best show the results of a survey of 14 people where 75 ride a bus, 45 drive cars, 15 carpool and 9 walk to work. Draw the graph. 2. State which type of variable is plotted on the x-axis and which type is plotted on the y-axis. 3. Explain why the points in a line graph are connected. 4. How are line, bar and circle graphs similar? 5. How are line, bar and circle graphs different? 6. Draw a line graph, circle graph and bar graph.