Finding and appraising qualitative evidence
Statistical Significance – CASP< Back to search results
- Format Websites
- Language/s English
- Target Audience Further education
- EBM Stage 3 - Appraising evidence
- Duration <5 mins
- Difficulty Introductory
Key Concepts addressed
In a well-conducted randomised controlled trial, the groups being compared should differ from each other only by chance and the treatment received. We can quantify chance, and so we can quantify the treatment effect in relation to it. If the difference between groups is large compared to the play of chance, we can conclude that the difference is probably due to the treatment; if it is small by comparison then we cannot exclude chance as the reason for the results.
The same statistical methods can be used for non-randomised research designs, but the interpretation is not as straightforward as for an RCT. This is because the measure of the effect is influenced by other factors which introduce bias and which cannot be fully accounted for in the analysis.