Presenting the results of your ANOVA.

When you write up the results of your statistical analysis in your dissertation or thesis or manuscript you can’t just present the p-value and claim you have a result. Instead you include summary statistics describing the data, a written description of what went up and what went down and you back this up by presenting the results of your ANOVA. For your typical one-way ANOVA you need to present what’s called the F-statistic and the Degrees of Freedom of your analysis, as well as the p-value. Here’s an example with two ANOVA results in bold:

The diameter of oocytes varied significantly between individuals from the three populations (F2,22 = 7.54, p < 0.01). Mature females from Froe Creek contained oocytes with a mean (±SD) diameter of 222.7 μm (±8.4). The Teign Estuary and Restronguet Creek females both had lower mean oocyte diameters with means of 206.5 (±14.1 μm) and 197.2 (±9.0), respectively. The Froe Creek mean was 108% of the Teign Estuary mean and 113% of the Restronguet Creek mean.

No significant differences were observed between the variances of the diameters measured in collected oocytes (F2,22 = 1.54, p = 0.239). The mean variance (±SD) of oocytes collected from Froe Creek individuals was 20.2 (±20.8), that of the Teign Estuary individuals was 20.2 (±11.7) and that of Restronguet Creek individuals 31.8 (±15.2).

Note that the letter ‘F‘ is capitalised and italicised, the numbers following it (the Degrees of Freedom) are subscript and separated by a comma, and the ‘p‘ is also italicised. Here’s an example of the output of a one-way ANOVA in R from the previous post on how to do an ANOVA in R. I have highlighted where each value appears.

anova-output-from-r

Finally, it’s important to remember that the p-value is an estimate and so, if you have a significant result (p < 0.05), it is customary not to present the actual p-value given by the ANOVA but to indicate instead that it is less than one of three arbitrary values: p < 0.05, p < 0.01 and p < 0.001.

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