GRAPHING TUTORIAL

When having to draw graphs and interpret data the starting point is making sure the correct axes are used. The independent variable goes on the X axis (horizontal axis) and the dependent variable goes on the y axis (vertical axis).

From designing our Fair Tests we know that the Independent Variable is the variable that we, as Scientists, change, making sure that we only use the 1 independent variable. As we change the value of the independent variable we observe what happens to the Dependent Variable. If we have designed a good Fair Test then there should be a relationship between the two; this is what we are testing. Time is often an Independent variable that is used with observations being observed for any changes in the chosen dependent variable over time.

For example we could look at changes in rate of growth of microorganisms on an agar plate over time. With all other variables being controlled, such as temperature, nutrient source, sterilisation etc then time which is obviously measurable is the independent variable and changes in growth is the dependent variable. If we changed the fair test to study the effects of different concentrations of disinfectant  on microorganism growth then the concentrations of disinfectant we have chosen, and measured, would be the independent variable.

Returning to graphs there are a number of types of graphs we can draw depending upon the type of data being analysed. Some of the most common include:

• Line Graphs
• Bar Charts
• Pie Charts

Generally the most common type of graph we will be concerned with plotting is a line graph which are particularly good for plotting data that changes over time, with time often being the independent variable, plotted on the x axis.For further information on different types of graphs press here.

The science buddies website has more useful information:
this page gives a good overview and lists key points when drawing up graphs!