During my manuscript review process, reviewer asked me to keep the exact p value rather than denoting < 0.05 or < 0.01. I had tried in graph pad prism and graph pad instat statistical software's to calculate the p value by using ANOVA test, but i didn't got exact p value. Any one can give your valuable suggestions to calculate exact p value. Its most urgent.
Thank you
Hi Pradeep,
Before calculating the p-value, it is important to know which test are you using. If you use z test, then the calculation is quite easy. If you use a value, say x, and standard deviation, y, whereas the total number of samples is n, then z is calculated,
z = (mean - a) / (s / (sort(n))
and p is calculated, p = 2*pnorm(-abs(z)). [for 2-tailed].
P value calculated from t-test requires to calculate degrees of freedom,
p = 2*pt(-abs(t),df=n-1).
Please use R for your statistical calculation, you'll find the exact p-value for any statistical test.
In general, if you know the distribution, it's test statistic links directly to a p-value. It is 1 - the integral of the PDF from -infinity to that value. Ditto to above: R will produce it for you.
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