Why 0.05?

Foundations of Inference in R

Jo Hardin

Instructor

Personal level of significance

 

$$P(H) = 1/2$$

Personal level of significance

 

$$P(HH) = (1/2)^2 = 1/4$$

Personal level of significance

 

$$P(HHH) = (1/2)^3 = 0.125$$

Personal level of significance

 

$$P(HHHH) = (1/2)^4 = 0.0625$$

Personal level of significance

 

$$P(HHHHH) = (1/2)^5 = 0.03125$$

Degree of skepticism

• Cutoff of 0.01 instead of 0.05 is more skeptical of observed results
• 0.05 is subjective
• Only significant results from well-designed studies should lead to further investigation

Let's practice!

Foundations of Inference in R