P Values

When is a P-value significant?

Alpha (false positive rate) sets the critical level of our P-value to accept or reject the null hypothesis. P < α = reject the null hypothesis (statisticlly significant finding) P > α = accept the null hypothesis

Interpret P = 0.04 and α = 0.05

As P < α we reject the null hypothesis. This difference between groups/time periods is stastically significant. However this does not mean that we prove the alternative hypothesis.

What is a P value?

When we test a null hypothesis, the probability of that event occurring is provided as a P-value. The smaller the P-value, the stronger the evidence against the null hypothesis.

What does a P value of 0.18 mean?

No evidence (>0.15/15%) to disprove the null hypothesis

How do you interpret a P-value?

Note ~ if there is strong evidence against the null hypothesis, the alternative hypothesis remains but isn't proven

What does a P value of 0.04 mean?

There is evidence (<0.05/5%) to disprove the null hypothesis

What does a P value of 0.004 mean?

There is extremely strong evidence (<0.01/1%) to disprove the null hypothesis