Question

If I was doing some critical research where the consequences of my results could mean the difference between life or death, which significance level would I want to choose and why?

Answer 1

If you were doing a critical research such that any consequences of your results could mean the difference between life or death, then you should use the significance level as small as possible, because if you use very small significance level, you will get more accurate decisions regarding to rejecting or do not rejecting null hypothesis. For this scenario, you should not use regular 5% or 1% level of significance. You should use 0.5% (α = 0.005) or less significance level. By doing this, you can minimize the type I error and type II error.