Graphing
- Click to view a checklist for completing graphs.
- Click to learn how to graph in Excel.
- Click to learn about interpreting error bars on graphs.
- Click to read a short article about the effective use of graphs.
How do I know which type of graph to use? Follow this key…
1. Is the data a percent that sums to 100% or a total amount of time?
a. If yes .…………………………………Pie chart
b. If no…………………………………....Go to #2
2. Are both your manipulated and responding variables quantitative?
a. If no………………………………….... Bar graph
b. If yes …………………………………. Go to #3
3. Is your manipulated variable levels continuous (i.e. time in years) or clumped into groups (i.e. 0-5 years, 6-10 years)?
a. Continuous…………………………... Scatter plot/line
b. Clumped .....…………………………. Histogram
- Mark the quantities on both axes and number them at regular intervals. Your axis intervals do not have to be the same on the x and y axis and they do not have to always start at the origin with a value of 0.
- Giving the graph a title. The graph must have a title which should contain a brief description of what is being investigated. Other information which may go in the title, if available, includes: the date, place and name of experimenter or collector of the data. If there is more than one graph a reference number or letter is required. For example: “Fig 2: A graph showing the change in testis weight throughout the year in the brown rat (Rattus rattus)” IS BETTER THAN... “A graph of testis weight against time” which is insufficient. Underline or use bold type for your title it makes it stand out and is easier to find on the page.
- Plotting more than one graph on a set of axes. Sometimes two or three sets of data (though rarely more) are plotted within the same set of axes. You must distinguish between them by using different symbols (X, Ο, , ∇ etc) or lines (…………., ________, -----------, etc). Use a key by the side of the graph which explains the symbols or lines. Do not write on the graph itself though labels and arrows may be useful. You may wish to plot data from two different responding variables together on one graph but the values may be so different you have to use two different scales. One axis can be placed on each side of the graph.