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Type 1 and Type 2 Errors Explained


In probability and statistics, there is a topic called "hypothesis testing". One can use hypothesis testing to make a decision. For example, to help determine if a medicine had some real effect.

With any decision to be made, you can make a correct decision or a mistake. There are two errors that statisticians focus on. These errors are called Type 1 and Type 2 (often written as Type I and Type II).

In this short article I describe a tense hypothetical situation (hopefully none of us ever have to go through) and share a graphic which I think explains these errors sufficiently and without further comment.

Situation: Consider someone breaking into your house at night. You happen to have a gun for self defense situations, and you jump out of bed and grab it. You head towards the sound...and then...

Was it actually a bad guy threatening your life? Or was it just your child sneaking in at night?

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