V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA It is nearly always the case that the most effective way of revealing the significance of experimental data is by graphical presentation. Graphs are the most effective way of expressing the relationship between experimental variables. They are also useful for illustrating curve-fitting and identifying outliers.

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA It is nearly always the case that the most effective way of revealing the significance of experimental data is by graphical presentation. Graphs are the most effective way of expressing the relationship between experimental variables. They are also useful for illustrating curve-fitting and identifying outliers.

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA Sample experimental data:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA Example of a poor graph: No units Axis range too large Axis label cluttered Horizontal grid only Background too dark Wrong label Title font too small Symbols too large Axis title missing Poor axis labelling Poor axis range

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA Example of an improved graph:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA Example of a graph with linear scales: Suggested model:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA And with logarithmic scales: Suggested model:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA Example of another graph with linear scales:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA And on polar scales:

V. Rouillard  Introduction to measurement and statistical analysis GRAPHICAL PRESENTATION OF EXPERIMENTAL DATA General Rules: Axes should have clear labels naming quantities, units and symbols if required. Axes to be clearly numbered at major tick marks Use engineering notation when necessary (ie: 50 x 10 3, 100 x 10 3, 150 x 10 3 instead of 50,000, 100,000 and 150,000. Better still use the accepted numerical prefix in axis title if possible ie: kilo then simple numeric for the labels: 50, 100, 150 …. When axes do not start at zero use an axis break to illustrate the fact: Use symbols such as for data points while ensuring that you use a legend if more than one symbol is used. Use error bars to indicate the estimate uncertainty of the measurement or, if possible, adjust the size of the symbol to reflect the uncertainty of the measurement. Theoretical of fitted curves should be plotted as lines. Use different line types to differentiate between curves. Include a graph title which should be descriptive but concise. Final hint: Spend time exploring the capabilities of the graphing software so you can exploit all available features