This time of year, most of the questions I get focus on **how to graph the data **collected. If you are trying to decide between a line graph and a bar graph… it usually is not your choice. The type of data and type of project dictate what, mathematically, you are “allowed” to do.

Here is a reminder:

**LINE GRAPH** – you must have **quantitative and continuous **data for **both **your independent and dependent variables. That is data that can be assigned a number that could be logically placed on a number line. For example, temperature, time, size, weight, wavelength, speed, etc. HOWEVER – if either of your variables are qualitative you CAN NOT use a line graph (even though your graphing program will let you!!). This is one of the biggest mistakes I see at science fairs.

**BAR GRAPH** – the overwhelming majoring of science fair projects are best presented with a bar graph. Usually that means you have a qualitative variable on the x-axis (horizontal) and a quantitative variable on your y-axis (vertical). Use bar graphs for all projects that have different “treatments”, for example: different conditions under which you pop popcorn, or freeze liquid, or bounce balls, or break eggs, or grow plants, or fly paper airplanes, etc. Use bar graphs too if you are varying colors (e.g. red vs. blue) or groups (e.g. male vs. female; different types of soda; different types of seeds; etc.).

With yes/no data (or counts):

—You might be able to make a pie chart showing the percentage of yes vs. no or

—You might be able to make a bar graph by calculating the number of yes (or no) divided by the number of attempts (or trials) and then you have a number for your y-axis. For example if you ask 20 women and a question and 10 answer yes and ask 20 men the same question and 5 say yes; then you could calculate the percentage of women who answered yes (10/20*100 = 50%) vs. the percentage of men (5/20*100 = 25%) and graph the percentage.

—The same applies to projects where you have “counted” the occurrence of something, for example the number of times the can floated; or flower died; or egg broke. Convert “counts” into percentages and make a bar graph or pie chart depending on your project.

**DON’T FORGET TO LABEL BOTH AXES with labels, units and numbers.** That is another very common mistake.

NickI am doing a experiment about how different amounts of weight effects how high a magnet can levitate. I am required to have two graphs, can you give me any suggestions

Dr. Maille LyonsBar graph with weight on x-axis (one bar for each weight tested); and whatever “measuring” regarding the magnet’s ability to levitate on the y-axis

Line graph: time on x-axis and whatever “measuring” regarding the magnet’s ability to levitate on the y-axis (one line per weight tested).

Elizabeth MaciejewskiWhat can I do I did dancing popcorn.

I put popcorn, RIce, Sugar, salt, and paperclips in the same amount of liquids to see what one “danced’ or moved. How can I chart it or use a graph?

Dr. Maille LyonsYou can only make a graph (or chart) if you measured sometime – so did you measure the time it took to start dancing? or the distance each item danced?

If yes, then make a bar graph with the item on the x-axis and whatever was measured on the y-axis. Otherwise – make a table with the item as the column and a yes/no in the box.

ArelinaI’m at a loss with how to do a graph. My son is in the 4th grade and the big question is What corrodes faster in a container of soda? (Glass shard, rubber band, paper clip) We’ve also had 3 separate trials #1 with coca-cola #2 with Sprite & #3 with Dr. Pepper. First we did the entire experiment at sea level at 76′ F. Then we did a second experiment using all the same items, new of course-just like the first one. Except this time we did the experiment in the fridge at 35′ F. The glass shard never corrodes In either temp. The rubber band got a tad larger in cola in both temps. And the paper clip corroded the fastest in cola. We saw corrosion within 24 hours in all 3 sodas so we kept the experiment going for 72 hours. Each day the paper clip getting more and more corroded. How do I put all of this data into a graph??? Please please help. Project is due In 1 week. I’ve got everything for it, I just don’t know how to put it all together & I do not understand the graphs. Your help would be greatly appreciated.

Dr. Maille LyonsYou have multiple independent variables: Type of liquid; type of material; temperature; time

But in order to make a graph, you need a quantitative dependent variable. Sounds like you have “time to observe corrosion” except that if you have “all” and “none” so the graph will be boring and not very informative. If you took photos and can measure “amount of corrosion” you could use that. Otherwise, you will be limited to presenting observations in a table. Make multiple tables so that each of the qualitative variables can be compared.

For example, for EACH temperature – make a graph with type of liquid as columns and type of material as rows; in each box present a photo and a description of the outcome

Deborah RobinsI had to do an experiment where we had 2 ziplock bags. We put 1tsp of yeast in each bag. Then we put 30 ml of hydrogen peroxide in bag A and 60 ml in Bag B for ten minutes. We measured the height of each bag at the end of the time. How should I graph this? Thanks

Dr. Maille LyonsBar graph with Amount of Yeast (tsp) on x-axis and Height of Bag (units) on the y-axis; one bar for bag A, one for bag B

Julia BeamonI have a question to ask about how to display my data. I did the experiment of making biogas from different vegetables as well as an empty bottle fir my control. I tested puréed onions, blueberries, lettuce a mixture of onions and bleach and a control ( empty bottle). After the substances were added to a bottle I quickly covered the bottle with s balloon and taped the balloon on the bottle to seal it. I then measured the size of the balloon and recorded my findings. I observed the bottles for seven days but after day one nothing much happened except the balloons eventually went flat because of pores in the balloons. I repeated the same experiment three times and found similar results each time. How do I show this information in a graph. Do I include three trials with five bottles. Each for seven days. I don’t know how to show all of this information in one graph not do I know what kind of graph to use. Please help

Dr. Maille LyonsBar graph. Type of veggie on x-axis. Size of balloon on day one on y-axis. Each veggie should have a grouping of three bars to represent 3 trials.

JenniferHello,

Thank You for all your information. My experiment is What recycled medium will oyster mushrooms grow best? I tried to grow the spawn in only coffee grounds, coffee grounds and cardboard, and coffee grounds and wheat straw. In all my research, it stated to place the containers in a dark place for a minimum of a week and a half. When I checked on them trail 1- they had all been over taken with mold(too much moisture). trail-2 to dry and parts were covered in mold. Currently on trail 3. What kind of graph can I make if all three are a failure and I get no growth.

Thank You

Dr. Maille LyonsSorry … no data will mean no graph. Did you take photos? You could present them as your “Results”