Light On Light Off
|
Hit |
False Alarm |
|
Miss |
Correct Rejection |
Response
of Yes
Response
of No
“Response of Yes” means the subject says that the light is on.
“Response of No” means that the subject says the light is not on.
Thinking about the detection of very soft sounds may make the understanding of these concepts easier. Imagine being in a totally sound-proof room. From time to time very soft sounds are briefly presented. Your task is to press a button every time you think you hear a sound.
Hit — sound on, you say it’s on
Miss — sound on, you say it’s not on (like “missing” a call because you didn’t hear the ring)
Correct Rejection – sound off, you say you didn’t hear anything
False Alarm – sound off, but you say you do hear a sound
Note that the terms (hit, false alarm, miss, correct rejection) sound like what they mean.
The loudness of the sound is — signal strength. Of course, the stronger the signal, the more likely you are to hear the sound when it is actually on (a higher hit rate and a lower miss rate).
How good your hearing is would be — sensitivity. Of course, the more sensitive your hearing, the more likely you are to hear the sound when it is actually on (a higher hit rate and a lower miss rate).
You can also be more or less cautious about saying that the sound is on — response bias. The important point about response bias is that if you are more cautious, hit rate will go down AND false alarm rate will go down. But if you are less cautious (if you say you hear something whenever you think there is any chance at all that the sound was on) then your hit rate will go up AND your false alarm rate will go up.
So — if you vary response bias, both hit rate and false alarm rate will change, and in the same direction. Less cautious = higher hit rate AND higher false alarm rate. Greater caution = lower hit rate and lower false alarm rate.
So — if you want the false alarm rate to be really really low, one consequence may be that the hit rate will also be very low.
With regard to jury decisions — that means that if jurors are really really careful to avoid false alarms (that is — really really careful not to say that an innocent person is guilty) then their hit rates will also be low (a low rate of saying that a guilty person is guilty).
