Unit 2 Lesson 1 Representing Data

Modeling Data with Graphs Unit 2 Lesson 1 Representing Data Modeling Data with Graphs How do scientists make sense of data? All of the different types of scientific investigations involve the collection of data. Data are the facts, figures, and other evidence scientists gather when they conduct an investigation. Scientists organize and record their data in data tables. Copyright © Houghton Mifflin Harcourt Publishing Company 2

How do scientists make sense of data? Unit 2 Lesson 1 Representing Data How do scientists make sense of data? Data tables often have two columns. One column lists the independent variable, which is the variable that is deliberately manipulated in an investigation. The other column lists the dependent variable, which is the variable that changes as a result of manipulation of the independent variable. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Data Table

How do scientists make sense of data? Unit 2 Lesson 1 Representing Data How do scientists make sense of data? Scientists often analyze data for patterns or trends by constructing graphs of the data. The type of graph they construct depends upon the data they collected and what they want to show. Copyright © Houghton Mifflin Harcourt Publishing Company 5

How do scientists make sense of data? Unit 2 Lesson 1 Representing Data How do scientists make sense of data? A scatter plot is a graph with points plotted to show a possible relationship between two sets of data. In a scatter plot, the horizontal x-axis usually represents the independent variable, and the vertical y-axis represents the dependent variable. To show the general relationship between the two variables, a “line of best fit” may be used. Copyright © Houghton Mifflin Harcourt Publishing Company 6

Scatter Plot

More Graphing! What do graphs show? Unit 2 Lesson 1 Representing Data More Graphing! What do graphs show? Scientists use different types of graphs to show different types of information about data. A bar graph is used to display and compare data in a number of separate categories. A circle graph is used to show how each group of data relates to all of the data. Copyright © Houghton Mifflin Harcourt Publishing Company 8

Throw Me a Curve! What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data Throw Me a Curve! What kinds of patterns can be shown using graphs? When you graph data, you can identify what the pattern, or trend, of the data is. A trend shows the relationship between the two variables studied in the experiment. Graphs make it easy to tell if something is increasing, decreasing, or staying the same. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data What kinds of patterns can be shown using graphs? In some cases, a line can be used to show the trend of data on a graph. If the relationship between the independent and dependent variables can be shown with a straight line, the graph is called a linear graph. A straight line shows that the rate of change of the dependent variable with respect to the independent variable is constant. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data What kinds of patterns can be shown using graphs? The density of water involves a linear relationship between mass and volume. Copyright © Houghton Mifflin Harcourt Publishing Company 11

What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data What kinds of patterns can be shown using graphs? A graph in which the relationship between the variables cannot be shown with a straight line is called a nonlinear graph. In a direct relationship, the value of one variable increases as the value of the other variable increases. The graph of a direct relationship is an upward sloping line. Copyright © Houghton Mifflin Harcourt Publishing Company 12

What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data What kinds of patterns can be shown using graphs? In contrast, an inverse relationship is one in which the value of one variable decreases as the other increases. The graph of an inverse relationship is a downward sloping line. Copyright © Houghton Mifflin Harcourt Publishing Company 13

What kinds of patterns can be shown using graphs? Unit 2 Lesson 1 Representing Data What kinds of patterns can be shown using graphs? The relationship between volume and pressure for a gas at a constant temperature is a nonlinear relationship. Copyright © Houghton Mifflin Harcourt Publishing Company 14

The Perfect Model How do scientists select a model? Unit 2 Lesson 1 Representing Data The Perfect Model How do scientists select a model? A model is a representation of an object or a process that allows scientists to study something in greater detail. The best models are those that most closely resemble the system, process, or object they represent. Copyright © Houghton Mifflin Harcourt Publishing Company 15

How do scientists select models? Unit 2 Lesson 1 Representing Data How do scientists select models? Scientists use many different kinds of physical and mathematical models. A physical model is something that is drawn or built, such as maps, globes, and dioramas. With mathematical models, you can predict the results of changes in a system. A computer simulation is one type of mathematical model. Copyright © Houghton Mifflin Harcourt Publishing Company 16

How do scientists select models? Unit 2 Lesson 1 Representing Data How do scientists select models? Scientists select a model based on the kind of information it shows and how it can be used. Today, many processes in science can be modeled in great detail. Copyright © Houghton Mifflin Harcourt Publishing Company 17