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NBME 21 Answers
A study is conducted on patients with asthma to ...
If the treatment really changes the mean asthma score by 0.4, there is an 80% chance that a study of this size will find a p-value < 0.05
I have a question : whats the relation then between power and P value ?
This one took me a minute and was during the last block so my brain was already fried. But my reasoning was that, as stated above, since it gave you power, it is basically just a long-winded way of asking what Power is, and how this relates to p-value. P-value is the odds that the finding was due to chance alone. Obviously a p-value set to <0.05 implies a greater than 95% chance that the finding is legit. Since the power is said to be 80%, this means that there is an 80% chance that the study finding is legit, at least insomuch that it met the pre-set criteria of being 95% non-chance related.
80% chance (power) the study correctly identifies the existence of an association in reality. If an association is determined to exist, >95% chance the study and reality agree with each other (p<.05)