What does “statistically significant” mean?
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- EBM Stage 3 - Appraising evidence
- Duration <5 mins
- Difficulty Introductory
Key Concepts addressed
- 3-3a Do the advantages outweigh the disadvantages for you?
- 2-3f Confidence intervals should be reported
Details
‘To be honest, it’s a tricky idea. It can tell us if the difference between a drug and a placebo or between the life expectancies of two groups of people, for example, could be just down to chance . . . It means that a difference as large as the one observed is unlikely to have occurred by chance alone.
Statisticians use standard levels of “unlikely”. Commonly they use significant at the 5% level (sometimes written as p=0.05). In this case a difference is said to be ‘significant’ because it has a less than 1 in 20 probability of occurring if all that is going on is chance.’
Spiegelhalter D, quoted in: Making Sense of Statistics. 2010. www.senseaboutscience.org
Read more in: What does a “significant difference” between treatments mean?
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