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Graphing 101

Once you have your data, you will need to present it to your teacher and science fair judges. In a science publication, you would choose between a table and a graph, but for the science fair project it is acceptable, and even encouraged, to showcase the data in both forms.

Type of graphs: Your first choice is to determine which type of graph would best communicate your findings. Your basic choices are bar graph, line graph, pie chart, or scatter plot.

BAR GRAPH – This is the most common type for science fair projects. You may select a bar graph when your independent variable is qualitative (categories) or quantitative (numbers).

An example of a bar graph

Look closely and make sure your bar graph has all the highlighted parts:

Independent variable may be qualitative or quantitative

LINE GRAPH – This is the second most common, but frequently used incorrectly, so be careful here. You should only select a line graph if your independent variable is quantitative (numbers) and you hypothesized that the changes in the independent variable would result in changes in the dependent one. For example, line graphs are great for showing changes in the dependent variable over time or distance along a transect.

An example of a line graph

Again double check the axes:

Independent variable MUST be quantitative

PIE CHART – Pie charts are good for projects that have qualitative independent variables and have generated data that can be expressed as percentages of the total. For example, if your data were counts (i.e. the number of times something happened), then this might be your best choice to compare different treatments.

An example of a pie chart

SCATTER PLOT – If the purpose is to see if the variables are related (common in environmental projects), but there was not a clear choice for independent and dependent variables (for example wind speed and water temperature), then a scatter plot would be your best choice. This option typically requires much more data than the others to observe a trend.

Scatter plots are also called X-Y plots


6 Responses to Graphing 101

  1. Chris Harrris

    This is Really Helpful

  2. Annette

    My daughter did an experiment to see which long stemmed flower would last the longest. What would be a good graph or is it possible to graph the results?

    • Dr. Maille Lyons

      Bar graph: flower type on x-axis; time on y-axis. Hopefully you had at least 3 flowers (e.g. 3 roses) for each flower type. Present photos if you have them to show when you decided the flower was “done”

  3. Melissa

    I’m doing an experiment on: How does the amount of water affect the growth of plants? I’m conflicted in which type(s) of graph I should use.

    • Dr. Maille Lyons

      You could do a bar graph, for each different volume of water used (x-axis) with the final growth (height? weight? number of new leaves? etc.) on the y-axis.

      You could also do a line graph with time on x-axis and growth on y-axis, using a different colored line for each volume used, if you measured growth over several time points.

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