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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


21 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.

  4. Desiree & Alaira

    We LOVE this idea…..our project is due in TWO MORE DAYZZZZ!!! and we didn’t even start on our projects yet because we didn’t know which one to pick…..and we have NEVER done a science project in our lives! the last part we needed was a chart to go with what our experiment was about….and all we wanted 2 say was thnk you! with love from Beaufort Middle School (South Carolina)

  5. Sophia Parker

    My son is doing a Science Fair Project on bacteria I have 8 different samples and 3wks of work what chart do you think I may need?

    • Dr. Maille Lyons

      What are the 8 samples?
      What did you measure?
      What do you mean by 3 weeks of work (i.e. what did he actually do?)

      Most likely a bar graph (based on 8 different types of samples), but potentially a line graph because time (3 weeks) is quantitative.

  6. Diego Morales

    I am doing a science fair project on if music can improve taking free throws in basketball and I don’t know what graph to use

  7. Zoe Moore

    Did a science project on which substances made metal rust. No time involved. All metal rusted in different solutions

    • Dr. Maille Lyons

      Did they all rust the same amount? What was your control (plain water – maybe?) Did the control also rust as much as the others? Do they look different in ANY way? What metal objects did you use? What solutions did you test?

      • Zoe Moore

        Thank you. The penny and nail and paper lip all rusted at different time frames. Control was water and it rusted as much as the others. Metal button rusted at different rate. We also had the nail in mud and it rusted. The penny and button had white and black on it. The nail had orange on it. The paper lip was just black

        • Dr. Maille Lyons

          Your best bet will be photos with a data table for your observations (i.e. what you described each as). There really isn’t anything to graph unless you can somehow estimate the percent coverage of rust.

  8. Aden

    I am doing a science fair project on changing the color of carnations. I am using red, blue and green dye.
    I will try to find which color is absorbed the fastest. LIght, amount of wate, temperature of water and the number of dye drops will all be the same. I dont have a clue as to how to graph this project. Any ideas? Please help!

    • Dr. Maille Lyons

      If you measure the time it takes to first see color and/or the time it takes to get a fully colored flower, you will be able to make a bar graphs for time vs. treatment (each color).

      Alternatively you could photo at the start, then 1 hour, 6 hours, 12 hours, 24 hours, then once each day until you don’t see any further color changes (or any other time periods you think are best). You will then be able to make a line graph with time on the x-axis and percent colored on the y-axis. You will have three lines (one for each color). You can estimate percent coverage from the photos and compare.

  9. Jack

    My science fair project deals with behavior science. I am testing about 10-20 people between the ages of 15-60. I want to know how to make a graph or chart showing how well people remember a short poem. I am documenting how many pauses and mistakes and if they have to start over. I do not know how to show my findings though. Please give me advice. Thank you.

    • Dr. Maille Lyons

      You could group the data by male and female and make a bar graph for number of mistakes (y-axis) vs. male/female.

      You could group the data by age (pick 5 or 10 year categories like: 15-20, 20-25, 25-30, etc.) and do the same as above.

      You could also make a scatter plot graph with age on the x-axis and number of mistakes on the y-axis to see if older trends toward more mistakes.

  10. Anita Rodriguez

    I am doing a science project on which gum is stickier, chewing gum or bubble gum. I measured the tack of the gum by sticking each piece of gum (each piece cut to 2 grams) “sandwiched” between two pieces of foam board. I pulled the foam board apart and measured how far it stretched (stuck together) until it fell apart, at which point i measured the distance in cm. At that point I also recorded the area that was still covered in gum and recorded the percentage of gum still stuck to the foam board. Is there another (or better way) to measure the stickiness of the gum? How would I put the data on to a graph?

    Your help is much appreciated!

    • Dr. Maille Lyons

      Sounds like you have already made the project your own and have quantitative dependent variables which is exactly what you want! Nice job.

      OK – for the graph, you can make at least 2bar graphs with Gum Type on the x-axis: 1 bar for chewing and 1 for bubble; then the y-axis will be Stickiness, measured as the length reached before breaking (in cm) = 1 graph and Stickiness, measured as the amount left stuck behind (in % still stuck) for the 2nd graph.

      If you want to do more work, you could also use your system, rigging a small cup/holder to the second board and see how much weight it can support before breaking (so instead of pulling up, let gravity pull down) – your metric would be the number of pennies (or other small weights) the gum can hold before breaking.

      You could also test more types of gum (e.g. different brands of each type) or if you can somehow get an estimate of sugar content you could compare “stickiness” vs. sugar content.

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