# P value and significance

I always get confused when to reject or support/fail to reject the null hypothesis given values for both. Is it like, whenever p values aree less than significance level we reject the null? Does this statement always hold true?

Thnks

p-value < (1-confidence intevall = significance level) than reject the null otherwise fail to reject the null. For visualization draw a schematic bell curve with a confidence intervall and then draw a p-value inside the confidence intervall (=fail to reject the null) and a p-value outside the confidence intervall (=reject the null). Best, Oscar

thnks

I agree with Oscar.

Does rejecting null mean you automatically accept the Alternate?

Yes, that’s the consequence.

I had a candidate give me a great way to look at p vs. α:

• α is the chosen level of significance
• p is the observed level of significance

You reject the null hypothesis (in favor of the alternative hypothesis) if the observed level of significance is less than the chosen level: p < α.

You fail to reject the null hypothesis if the observed level of significance is greater than the chosen level: p > α.

I always over thought this one, but it is really simple. If the p value (decimal from 0-1) is less than 1- confidence interval, you reject the null.

So if confidence interval is 95% you reject all p values below 0.05.

Unless I am wrong, then this was not helpful

do you mean you fail to reject the null if the observed level of significance is GREATER than the chosen level: p>a? otherwise, wouldn’t your statement be the same as the one right above it?

Yup.

I’ll correct it.