The language of statistical significance

There is a fair amount of language that we wrap around this process. We talk in terms of a test of significance. If p 0.05, we declare statistical significance, and reject the null hypothesis at the 5 per cent level. We call 5 per cent the significance level, it is the level at which we declare statistical significance. If p 0.05, then we say we have a non-significant difference and we are unable to reject the null hypothesis at the 5 per cent level. 

Our conventional cut-off for statistical significance is 5 per cent but we also use other levels, notably 1 per cent and 0.1 per cent. If p 0.01 then the evidence is even stronger that there are differences and we have highly significant differences. If p 0.001 then the evidence is even stronger still and we have very highly significant differences. 

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