Graphing Data

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Graphing Data

• A key skill for any scientist

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What types of graphs do we know?

• Bar graphs
• Pie graphs
• Line graphs
• Scatter plots

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What are these graphs used for?

• Bar chart to compare quantities of some
  variable on one graph.

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Pie Charts

• Pie charts are used to represent percentages.

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Line Graphs

• Line graphs are used to represent a change in
  variable over time.

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Scatter Plots

• Scatter plots are used to represent changes in
  two variables.
• In scatter plots, the points are NOT connected

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Graphing Checklist

• Appropriate title
• Axes
• Drawn with a straight edge (or use graph paper)
• Arrow at the ends
• Appropriately labeled x and y
• Labeled with appropriate information (variable
  names and units
• Tick marks consistently labeled.

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Graphing Checklist, continued

• Appropriate scale graph should take up all
  space available.
• Correctly plotted data.

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There are 4 Steps to creating a proper coordinate
graph

• Select 2 variables.
• Select an axis to represent each variable.
• Select a scale for each axis.
• Plot the data points.

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Variables

• Variables are measurable quantities that can
  change during an experiment.
• Variables come in two types
• Independent variables
• Dependent variables

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Step 1 Variables

• Select 2 variables. This means you need to know
  what you are plotting.
• Be sure to note your units!!

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Independent Variables

• Independent variables quantity that YOU control
  
• Can sometimes be time
• ALWAYS goes on the X-Axis

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Dependent Variable

• Dependent variable quantity that is directly
  affected by changes in the independent variable.
• Is ALWAYS on the Y-AXIS

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Step 2 Axes

• Select an axis to represent each variable.
• X-axis----horizontal---is ALWAYS the independent
  variable.
• Y-axis----vertical---is ALWAYS the dependent
  variable.
• Remember to include your units

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Step 3 Scale

• Select a scale for each axis.
• Look at the smallest number, look at the largest
  number.
• What is the difference? (subtract)
• Decide how to divide that difference so it will
  fit.
• DIVISIONS MUST BE OF EQUAL VALUE!

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Step 4 Plotting

• Plot your data points correctly.
• (x, y)
• b. Find the horizontal value (x) then (y)mark
  your data point on the grid.

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Title of your Graph
y-axis
Dependent variable (units)
x-axis
Independent variable (units)
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Now, Its Your Turn

• Try plotting your data from the clothes pin lab.
  
• Follow all 4 Steps to earn maximum points.
• Include your graph with your lab sheet for full
  credit.