What does p value 2.5e-0.5 mean? If it is 2.5 × 10 ^0.5 then it is way above the statistically significant p<0.005.. learning this to interpret the results of one study..
1 Answer
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Taking 2.5e-0.5 at face value, that's $2.5 \times 10^{-1/2} \approx 0.79$ (as pointed out by @Dougal and @Repmat in the comments). The p-value is defined as "the probability of seeing a result as strong as observed or greater, under the null hypothesis."
Combining these two, we have the following: under the null hypothesis, the probability of seeing a result as strong as observed or greater is about 79%. So, given the null hypothesis, the result you have found is not particularly "unusual."
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6$\begingroup$ I don't think I have ever seen a computing system in which "2.5e-0.5" would even be considered syntactically correct. $\endgroup$– whuber ♦Jan 29, 2017 at 22:23
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$\begingroup$ @whuber, I haven't either. I use STATA, and if p were equal to 0.79, it would just report 0.79. That said, hopefully OP knows what how to define a p-value now. $\endgroup$– PeterJan 29, 2017 at 23:36
e-0.5? That would presumably mean $2.5 \times 10^{-0.5} = 2.5 / \sqrt{10} \approx 0.79$, but that's very unusual use of notation. Maybe it's a typo/mistake in the study. $\endgroup$2.5e-5would be much more standard, which would should be read as a computer version of scientific notation, i.e. $2.5 \times 10^{-5}$, which is a pretty small $p$-value. $\endgroup$