Whats the percentage that metal detectors actually detect contraband.

[Oska]

Is it like 66 percent detect rates because i've noticed it only picks up 2 of every 3 items that gets past when I exame contraband in the past 24 hours on my intelligence screen. Is there like an actual formula? Any insight is much appreciated

[jasonharris2]

its like50/50 so i use detectors at all the doors so if it gets by 1 the 2nd one will find it

[Frazzledragøn the Trustworthy]

It's not even close to the low chance of 50%. I'm not even sure if it actually can fail, though I'm saying that because I don't know specifics on the actual chance, so it is quite possible that it is about 85%, just as an example.
However!
After detecting contraband (or a false positive) the metal detector will shut down for a few seconds.
If a prisoner with contraband walks through during that time there is no alert.
If you don't have a guard in the area to hear the alarm then the prisoner will not be searched.
If your guards are too busy to search the prisoner quickly enough he might hide or sell the contraband before staff can look for it.

[Anen]

Originally posted by jasonharris2:

its like50/50 so i use detectors at all the doors so if it gets by 1 the 2nd one will find it

This is not how probabilities work. You multiply, not add.
So 50% to fail times 50% to fail is a 75% chance to find the item with 2 doors.