You'll have to read about each multiple testing correction technique, whether it be False Discovery Rate (FDR)
or Family-Wise Error Rate (FWER
). (Thanks to @thelatemail for pointing out to expand the abbreviations).
Bonferroni correction controls the FWER
by setting the significance level alpha
to alpha/n
where n
is the number of hypotheses tested in a typical multiple comparison (here n=3
).
Let's say you are testing at 5% alpha. Meaning if your p-value is < 0.05, then you reject your NULL. For n=3
, then, for Bonferroni correction, you could then divide alpha
by 3 = 0.05/3 ~ 0.0167 and then check if your p-values are < 0.0167.
Equivalently (which is directly evident), instead of checking pval < alpha/n
, you could take the n
to the other side pval * n < alpha
. So that the alpha
remains the same value. So, your p-values get multiplied by 3
and then would be checked if they are < alpha = 0.05 for example.
Therefore, the output you obtain is the FWER controlled p-value
and if this is < alpha (5% say), then you would reject the NULL, else you'd accept the NULL hypothesis.
For each tests, there are different procedures to control the false-positives due to multiple testing. Wikipedia might be a good start point to learn about other tests as to how they correct for controlling false-positives.
However, your output of p.adjust
, gives in general multiple-testing corrected p-value
. In case of Bonferroni, it is FWER controlled p-value. In case of BH method, it is FDR corrected p-value (or also otherwise called q-value).
Hope this helps a bit.