# interpretation of Significance level (Type I error probability) from pwr.t.test()

I was looking at the sig.level=Significance level (Type I error probability) from https://www.rdocumentation.org/packages/pwr/versions/1.3-0/topics/pwr.t.test

Can someone please explain me is Significance level (𝛼) equal to P value or FDR or what is relation between ?

I know that FDR depends on the p-value threshold and also on the truth and that False discovery rate (FDR) is the expected proportion of Type I errors.

if Type 1 Error Rate = "Probability of rejecting the null if it's true" = p-value threshold

and

Type 1 Error Rate = False Discovery Rate IF the null hypothesis is true and probability of making Type I error is 𝛼.

Also if my 𝛼 is 0.05 which means that that I want the probability that a null finding will be called significant to be less than 5%. In other words, I want the probability of a type I error, or a false positive, to be less than 5%.

How then do I explain 𝛼 in relation to p value or FDR?

• It is $\alpha$.
– Dave
Aug 3, 2020 at 16:49
• Thanks Dave, I edited it Aug 3, 2020 at 16:51
• So is your question about the relationship between $\alpha$, false discovery rate, and p-value?
– Dave
Aug 3, 2020 at 16:57
• Yes, indeed that is my question Aug 3, 2020 at 17:08