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Signal Detection Theory
AP Psychology · Unit 3: Sensation & Perception
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d′:
-
Criterion:
-
Hit Rate:
-
FA Rate:
-
Signal Present
Signal Absent
Say "Yes"
Hit
-
False Alarm
-
Say "No"
Miss
-
Correct Reject
-
Signal Strength (d′)
1.5
Criterion Position
0.75
Noise Spread (σ)
1.0
Scenario
Balanced
Liberal (say yes)
Conservative
High d′
Display
Area Shading
ROC Curve
SDT Analysis
Quick Quiz
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1. A "hit" occurs when:
No signal, person says "Yes"
Signal present, person says "Yes"
Signal present, person says "No"
No signal, person says "No"
2. A liberal criterion means:
High hit rate AND high false alarm rate
Low hit rate AND low false alarm rate
Only correct rejections
Zero false alarms
3. d′ (d-prime) measures:
Response bias
Sensitivity — ability to distinguish signal from noise
Reaction time
Absolute threshold
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