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(P < 0.05) meaning in effectiveness of a product
What does (P < 0.05) mean when the effectiveness of a product is compared to another?
For example
In one study reductions in wrinkle depth were observed by expert assessment at both 4 and 8 weeks for the salicylic acid containing formulation compared to its placebo (P < 0.05). -
4 Replies
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It means that the probability for the treatment being identical with placebo is quite small. Whether or not the statistical test used to obtain that p-value was the right one and whether or not the threshold of α=5% indicates a significant difference between the two groups remains questionable.Furthermore, even a very small p-value can be regarded as insignificant, for example when the confidence interval of the treatment group is so large that it encloses the placebo group.You have to read and understand a publication to be able to tell if there really is a difference. It’s all too easy to cheat with statistics. -
@Pharma so a treatment with (P < 0.01) is better than (P < 0.05). Am i correct?
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@Abdullah - I don’t know if it is “better” but that does mean the difference is less likely due to chance alone.
Think of it this way. p = 0.05 means if you conducted the same experiment 100 times, 5 of those experimental results are the work of chance alone. If p = 0.01 then only 1 time out of 100 would you expect the result to be due to chance alone.
p = 0.05 = 1 in 20
p = 0.01 = 1 in 100For comparison, when they wanted to verify the existence of the Higgs Boson particle, they required to results to be accurate within p =3×10^-7. That means 1 in 3.5 million.
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@Perry thanks ????
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