There can always be be unknown variables influencing the outcome of the experiment.
The key to determining if a treatment had an effect is to measure the statistical significance.
There are a number of different means of measuring statistical significance.
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The one used will depend on the pop in of research design that was used for the experiment.
Skelly AC.Probability, proof, and clinical significance.Evid Based Spine Care J.
2011;2(4):9-11. doi:10.1055/s-0031-1274751
