GRAPHING TECHNIQUES

All graphing must be done by hand, not computer!

Here is a checklist for graphing:

(1) Should the data be graphed as a line graph or a bar graph?

1. BAR GRAPHS are for comparing different categories of some variable/factor. For example, if you were comparing the numbers of eggs in the nests of different bird species, you would use a bar graph. If you were comparing the amount of rainfall in different cities, you would also use a bar graph.
2. LINE GRAPHS are for following a change in a variable/factor over time. For example, a line graph would be used if you were recording the temperature at different times of the day, or if you were recording someone’s height as he/she grew up from childhood to adulthood.

(2) Title

1. Does the title describe the data? Is it complete?
2. Very often the title is, “What is the Effect of ________ (indep. var.) on _________ (dep. var.).”

(3) X axis

1. The INDEPENDENT VARIABLE is plotted here. This is the variable/factor that the scientist decides to study. It is usually the first column of data in the data table.
2. Independent variable’s name? (e.g., “Area of hole”)
3. Units? (e.g., “cm²”)
4. Consistent multiple? (e.g., counting each line by 1’s, 2’s, 5’s, 10’s, etc.)

(4) Y axis

1. a. The DEPENDENT VARIABLE is plotted here. This is the variable/factor in the experiment that DEPENDS on the other variable. For example, the “Time needed to empty [the] bucket” DEPENDS on what size hole you have. The DV is usually the second column of numbers in the data table.
2. Dependent variable’s name? (e.g., “Time”)
3. Units? (e.g., “sec.”)
4. Consistent multiple? (e.g., counting each line by 1’s, 2’s, 5’s, 10’s, etc.)

(5) Plotting of data

1. If you can calculate averages, plot them, not individual trials.
2. Is the data accurately plotted as the tops of the bars (for bar graphs) or as points (for line graphs)?
3. For a line graph, is the line drawn, and is it drawn accurately? If there aren’t too many points, you could draw a line to connect all the data points. On the other hand, if there are a lot of points, you could draw a line of best fit, making a line go up the middle of all the data, with about half of the data points above the line and half below the line.

(6) Key/Legend -- If needed, is there a key/legend explaining any different colors or patterns that you have used in your graph?