Graphing Guidelines

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Graphing Guidelines

• Often the goal of an experiment is to find the
  relationship between two variables.
• As one variable changes, so does the other.
• Graphing is a useful way to visualize and
  describe these relationships.
• Because the use of graphs is so common in
  sciences, it is important for you to know how to
  construct and interpret graphs.
• When preparing graphs for this class, keep the
  following guidelines in mind

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Graphing Guidelines

• It is done on graph paper.
• Use the x-axis for the independent variable (the
  variable changed by the experimenter) and the
  y-axis for the dependent variable (the variable
  being measured).
• The scale you select should be easy to work with
  such as one square represents 1, 2, 5, or 10 or
  five squares represents a unit of 1, 10, or a
  multiple of ten (20, 100, 0.1). Never change the
  scale along an axis. However, you may use a
  different scale for each axis.

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Graphing Guidelines

• Select a scale that uses the greatest portion of
  the paper. Leave enough room to title your axis
  and graph.
• Label what the axes represent by including the
  measurement and its units. For example "Length
  (cm)" or Time in seconds

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Graphing Guidelines

• For line graphs, plot your points. Sometimes you
  will be asked to connect the dots.
• Other times you will be asked to draw the line of
  best fit. The line should pass as close as
  possible to each of the points but should not be
  connected point-to-point. If the relationship
  appears to be linear, the line of best fit should
  be a straight line.

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Graphing Guidelines

• Title the graph. Make sure you describe what is
  represented on the horizontal and vertical axes.
• If you are plotting more than one curve on the
  same graph, include a legend that identifies the
  curves. Use different colors or different types
  of lines such as solid or dashed lines between
  them.

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Example Graphs
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Practice Graphs

• Recall that a bar graph is useful for comparing
  information collected by counting. We are going
  to use the clothing of students in this classroom
  to demonstrate how to make a data table and bar
  graph. We will look at the shirt color of boys
  and girls in the room.

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Practice Graphs

• Step 1 Gather Data
• An easy way to organize our data is to create a
  table. Lets use this table to fill in our data.
  

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Practice Graphs

• Step 2 Create the Graph
• Independent variable (x-axis) ________
• Dependent variable (y-axis) __________
• Choose two different colors to use (one to
  represent boys, one to represent girls).

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Key Features of Bar Graphs

• Title
• Axis are labeled with units
• Legend
• Check your graph to make sure you have these
  three features

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Line Graphs

• Recall that line graphs are useful for showing
  trends.
• Problem
• In an experiment, you check the air temperature
  at certain hours of the day. At 8 A.M., the
  temperature is 27 ?C at 10 A.M., the temperature
  is 30 ?C at noon, the temperature is 32 ?C at 2
  P.M., the temperature is 31?C and at 4 P.M., the
  temperature is 30 ?C. Graph the results of your
  experiment.