Graphing Data

Displaying and Analyzing DataThe best method for displaying and analyzing data is

through the use of graphs

Graphing is an important procedure used by scientists to easily compare multiple variables.

There are many types of graphs, but the three most common kinds are line graphs, bar graphs, and pie charts

-- In this class, we will be primarily using line graphs and bar graphs

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What type of graph?

• You may wonder; How do I know which type of graph to use?– Line graphs are not just for time graphs!!!– Use a line graph when you have 2 quantitative

(number) variables• Ex. Speed vs. engine size

– Use a bar graph when you have one qualitative variable and one quantitative variable

• Ex. Migration distance vs. bird species

Find out now!! Click Here!

1. Draw and label the x-axis and the y-axis

-- the x-axis is the horizontal axis and the y-axis is the vertical axis

2. Label what variable is on each axis

-- the independent (manipulated) variable always goes on the x-axis and the dependent (responding) variable always goes on the

y-axis

Creating a Graph

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Independent Variable

Creating a Graph3. Decide which intervals you will be using on each axis and

write those in– Be sure that the intervals are appropriate for your graph

• Ex. 1 – If your dependant variable has values ranging from 5cm to 600cm, an interval of 5cm might not be enough

• Ex. 2 – If you are measuring the growth of a plant each week, you shouldn’t use meters on your graph y

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Creating a Graph4. Plot the data points that you collected on the graph.

5. If the graph is a line graph, connect the points with as smooth a line as possible.

6. Give your graph a title– Usually, the title of a graph is similar to the variables being manipulated and

measured. y

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Bob’s Weight Change Over Time

Graphical Analysis

• Remember that the reason for creating graphs is to help us to better visualize what has occurred.– You should always look at your graph after

you make it and consider what it is telling you• What is the general trend in the data? What is the

relationship between the variables? Does it make sense?

Final Questions

Bar Graph – brand is a qualitative variable, mileage is quantitative

Question 1

• You run an experiment to test how the brand of gasoline used effects your cars gas mileage. When you graph the data:– What type of graph would you make?

– Which variable would go on the x-axis? Why?

– Which variable would go on the y-axis? Why?

Answer

Answer

Answer

The brand would go on the x-axis because it is the independent variable

The mileage would go on the y-axis because it is the dependant variable

Question 2

• You measure the height of everyone at GM and create a graph of average height for each age from 14 to 18– What type of graph should this be?

– What trend do you expect to see in the data?

Answer

Answer

This should be a line graph because both variables are quantitative

The graph should have a positive (upward) slope. As students get older you would expect their heights to increase.

Remember to write out 2-5 questions about the notes for class!!