Graphing

What sport is most popular? Why do we graph data? What sport is most popular?

Reality Is there a trend in location and cancer? Where is unstaged colon cancer most common? Is there a trend in location and cancer?

Predicting Data on a Graph Graphs are a useful tool in science. The visual characteristics of a graph make trends in data easy to see. One of the most valuable uses for graphs is to "predict" data that is not measured on the graph. Extrapolate: extending the graph, along the same slope, above or below measured data. Interpolate: predicting data between two measured points on the graph.

What do Graphs Tell You? A graph is a way of expressing a relationship between two different variables. There are several types of graphs Line Graph Bar Graph (Histogram) Pie Chart Pictograph

Circle graphs show percentages of the whole The Uses of Graphs Circle graphs show percentages of the whole Coconut

Bar graphs show comparisons. The Uses of Graphs Bar graphs show comparisons.

The Uses of Graphs Line graphs show changes over time or the change of one variable (dependent variable) due to the change of another variable (independent variable).

Variables Variable: factor that changes in an experiment. Every scientific investigation has variables: Variable: factor that changes in an experiment. Independent variable: variable that is manipulated (changed) in an experiment. Dependent variable: variable that is affected by the independent variable. Example: In an experiment where we are looking at the effect of the amount of sunlight on plant growth, since we are manipulating the amount of sunlight, it is the independent variable and the growth of the plant is the dependent variable.

How to Construct a Line Graph Identify the variables Independent variable -Goes on the X – axis (horizontal) and is usually found on the left side of a table Dependent variable -Goes on the Y – axis (vertical) and is usually found on the right side of a table.

How to Construct a Line Graph 2. Determine the scale of the Graph Determine a scale (numerical value for each square) that best fits the range of each variable Always start at zero. Not starting at zero is considered to be dishonest. If the graph won’t fit the entire space by starting at zero use a symbol to indicate skipped numbers. Spread the graph to use MOST of the available space. The scale must always be evenly distributed, but doesn’t have be the same for the two axis. This is the main reason we generally graph in pencil. You sometimes have to erase when figuring this part out. Count it out in your head before writing anything down.

How to Construct a Line Graph 3. Number and Label Each Axis a. This tells what the lines on your graph represent. Label each axis with a title and the appropriate units. Number on the lines for a line graph (unlike in a bar graph when on the x axis you number in the spaces.) 4. Plot the Data Points a. plot each data value on the graph with a dot. 5. Draw the Graph a. draw a curve or line that best fits the data points. b. Most graphs of experimental data are not drawn as “connect the dots”. 6. Title the Graph a. Your title should clearly tell what the graph is about. b. If your graph has more than one set of data, provide a key to identify the different lines.

Directly Proportional and Inversely Proportional Graphs As the independent variable increases, the dependent variable increases as well. As the independent variable increases, the dependent variable decreases.

Why Draw a Line of Best Fit? A line of best fit emphasizes the overall trend shown by all the data taken as a whole.

Slope (Rate of Change) The slope (rate of change) of a graph line tells you how much y changes for every change in x.

Car Travel The graph shows the distance a car travels in a one-hour period. Use the graph to answer the questions that follow.

Car Travel Reading Graphs: What variable is plotted on the horizontal axis? The vertical axis? Time (min), the manipulated variable, is plotted on the horizontal axis. Distance (km), the responding variable, is plotted on the vertical axis.

Car Travel Interpreting Data: How far does the car travel in the first 10 minutes? In 40 minutes? The car travels 10 km in 10 minutes and 40 km in 40 minutes.

Car Travel Predicting: Use the graph to predict how far the car would travel in 120 minutes. Assume the car continues to travel at the same speed. The car is traveling 1 km per minute. It would travel 120 km in 120 minutes.

Car Travel Calculating: Calculate the slope (rate of change) of the graph. What information does the slope provide? The slope (rate of change) is 1 km/min. The slope (rate of change) provides information about the car’s average speed.

Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.

Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.

Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.

Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.

Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.