Psychology Study Group for the EPPP

✅ Understanding Type I & Type II Errors (Made Simple)

In research (and in life), we sometimes make mistakes when deciding what is true or false. Here’s an easy way to remember:

👩‍❤️‍👨 The Good Wife = The True Relationship (Null Hypothesis is True)
👩‍🦱 The False Ex = The Wrong Relationship (Null Hypothesis is False)

There are 4 possible decisions:

1️⃣ ✅ GOOD DECISION – You keep your good wife (you don’t reject a true null hypothesis).
2️⃣ ✅ GOOD DECISION – You reject your false ex (you reject a false null hypothesis).
3️⃣ ❌ TYPE I ERROR – You reject your good wife (you reject a true null hypothesis; false positive).
4️⃣ ❌ TYPE II ERROR – You don’t reject your false ex (you fail to reject a false null hypothesis; false negative).

🔹 Type I = Alpha error = False alarm (thinking something is wrong when it’s not).
🔹 Type II = Beta error = Missed detection (failing to see something is wrong when it is).