Type I and Type II Errors: A Trick to Remember Which Is Which

In statistics, a type I error is when you reject the null hypothesis when you should not; a type II error is when you accept the null hypothesis when you should not**. No owner of a normal brain can remember which is which without problems. Ethan Fosse posts a mnemonic which is supposed to help, but it doesn't work for me. Neither do any of the alternatives suggested in the comments. So I came up with my own. Here it comes.

The null hypothesis is often represented as H0.* Although mathematicians may disagree, where I live 0 is an even number, as evidenced by the fact that it is both preceded and followed by an odd number. Even numbers go together well. An even number and an odd number do not go together well. Hence the null hypothesis (even) is rejected by the type I error (odd), but accepted by the type II error (even).**

*Also, "null" means "zero" in German, but you don't really need that.

**Added: O.k., o.k., you don't actually accept the null, you just fail to reject it.


Stuart Buck said...

My take on that issue: http://stuartbuck.blogspot.com/2009/03/type-i-and-ii-errors.html

Anonymous said...

Thanks -- helpful!

Dr Judy's True Confessions said...

Sorry SBuck, I can't open your blogspot.

Mnemonics for english speaking statistical logicians.

Type 1 error is reject the null
Type 2 error is accept the null
"Accept" has a double consonant in the middle, so it refers to type 2 errors. Two "C"s =type 2
"Reject" has only one consonant in the middle, so it refers to type 1 error. One "J"=type 1 error


Caleb Bryant said...

Helpful. I'm being tested over it tomorrow

Rashidah (Hussains Mom) said...

-Reject that ONE good guy when I really should marry him. :)
-Accept the SECOND rate guy when I really should reject him.