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## Health and medicine

### Course: Health and medicine>Unit 8

Lesson 5: Sensory perception

# Signal detection theory - part 2

Created by Ronald Sahyouni.

## Want to join the conversation?

• if d'=1 B=2, D=b'- B, then shouldn't D= 1-2??
• So apparently, B is just an arbitrarily chosen threshold. The mistake he made (I think) is that he decided to change the value for B just for strategy D, simply because d' already equaled 1, and he just decided to change it randomly. For the rest of the strategies, he observed B = 2 as he had originally started.
• What are you talking about?
• This video might be helpful.

• C = A measure of the observers ability to correctly identify a stimulus (e.g. a sight, a sound.... w/e), based on a given "signal", in the presence of and equally present "noise" (overlapping but undesired/interfering stimulus). "B" is just a quantitative value for where (on an intensity scale) that individual can differentiate the signal from the noise. d' is just a measure of how similar the signal and the noise are.
• I am a bit confused with this video: I understand the separate entities( i.e. c,d, beta, and b) however I am confused how it all comes together. Could you post another video explaining this topic further?
• Having done a little more research on this...
1.) Should the ideal beta equal 1, not 0?
2.) Should the "signal" distribution actually be labeled "signal + noise"?
3.) At , you say you are choosing a "threshold"... Is this "threshold" a beta value or a C value?

Sorry for all the questions. I'm just frustrated because I've been stuck on this topic while studying for the 2015 MCAT for 4 hours now and am feeling like I'm having to dig a bit deeper than necessary to grasp this concept.
• This is a terrible video, please take it down or redo it
• love khan, but this one very confusing