Some Graphing Help…

Graph drawing is an essential science skill. There are some conventions that you should follow and some ideas that I would urge you to consider. Graphs can show trends in data and help you to predict possible future outcomes. The more data you collect the more accurate your graph is likely to be, allowing you to draw a line that follows the trend closely.

Unless you are told otherwise, plot the independent variable’s data on the x-axis (horizontal). This will be the variable that was being altered in the experiment to see what happens. The dependent variable data goes on the y-axis (vertical). This is the outcome of the experiment that is being measured. You must remember to label each axis and include the units.

Try to spread the data out along the axis in a sensible way – you want the points to be easy to plot. Also, don’t include too many numbers as the axis will become cluttered and hard to read. Plot your points with a sharp ‘×’ or ‘+’. I prefer the ‘+’ because it clearly defines the vertical and horizontal values.

When all the data have been plotted you need to decide whether to draw a curve through the points or a straight line. It takes some practice to consistently get this right. Look carefully at the trend the data are showing – the line needs to describe the pattern of the points. If one or two points seem to be out of alignment ignore them to follow the majority of points. Experimental errors often lead to slight inaccuracies in the results and you may be asked to ‘circle the faulty result’.

The example below shows the key points, including a point that has been left out and circled.

This video demonstrates the power of graphs to show trends. Whilst it is of a very modern, interactive graph, its basic principles apply to the graphs that you draw. It also happens to be very interesting in showing the relationship between national wealth and life expectancy.

Other posts here that might be helpful are…

Distribution Graphs

Drawing Graphs