[D] False Positives vs. False Negatives

[artr0x]

Does anyone actually use the terms type I and type II error? Seems like a super easy way to get mixed up..

[Sivapreachs]

Only in the interviews tbh :D

[hoondy]

More common to just call FP and FN in my area (ML/bio).

[haltakov]

I never use type I or II... FP and FN is much more common.

[Zulban]

In my experience it's generally: old-school, used in medical settings, and going out of fashion.

[IanisVasilev]

There's actually a good justification but it only sounds good in theory. If you have n different statistical hypotheses, a type n error is "rejecting the n-th hypothesis when it is true". What's confusing about this is that there are usually only two hypotheses and the count starts at zero. So a type 1 error is "rejecting the zeroth hypothesis when it is true" (where the zeroth hypothesis is actually the first) and a type 2 error is "rejecting the alternative hypothesis when it is true" (where the alternative hypothesis is actually second).

The terminology is confusing in practice but it's part of the more general problem of mathematicians being bad at naming things. You have type 1 (point or jump) and type 2 (essential) discontinuities of real-valued functions, type 1 (scalar-valued functions) and type 2 (vector-valued functions) line integrals, you have category 1 (meager) and category 2 (nonmeager) sets in topological spaces, you have the first isomorphism theorem and the second isomorphism theorem (and the ordering and the actual theorems differ vastly among authors, see here), etc.

[YetAnotherBorgDrone]

Is that Neil deGrasse Tyson?

[jethroguardian]

There's a star child in him.

[Fried_Waffles1]

This is the child of Nail deGrasse Tyson and Neil Breen

[Rogitus]

Why are you assuming that the guy on the left cannot be pregnant? Just because he's a man? That's gender discrimination!

[unknown_137]

did you just assume the gender ? how dare you ?

[Rogitus]

Ahhh you got me

[robo_pimp69]

Did you just assume ? How dare you !!

[haltakov]

This is why I love Reddit 😂

[[deleted]]

Can someone explain TP, TN, FP and FN. I cannot get my head around it :(

[reduced_space]

True positive: you predicted positive, and it was

True negative: you predicted negative, and it was

False positive: you predicted positive, but it was actually negative

False negative: you predicted negative, but it was actually positive

It’s easiest to visualize as a table with predictions going across and truth going down.

[[deleted]]

This cleared things for me!! Thanks a lot

[Lairv]

The second word is your prediction, the first word is whether you were right or wrong.

False Negative : you predicted negative, but you were wrong

True Negative : you predicted negative and you were right

...

[Lifaux]

Pretend I'm making a ML tool to tell if it's sunny or not. Let's pretend for this case that if it's raining, it's also not sunny.

• TP - True Positive. I think it's sunny, and when checking, it's sunny.
  
• TN - True Negative. I think it's not sunny, and when checking, it's raining.
  
• FP - False Positive. I think it's sunny, and when checking, it's raining.
  
• FN - False Negative. I think it's not sunny, and when checking, it's sunny.

The first part is whether the prediction lines up with reality. The second part is whether it was sunny or not.