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Pattern
Classification
All materials in these slides were taken
from
Pattern Classification (2nd ed) by R. O.
Duda, P. E. Hart and D. G. Stork, John Wiley
& Sons, 2000
with the permission of the authors and
the publisher
Pattern Classification, Chapter 2 (Part 2)
2.8.3 Signal Detection Theory
and Operating Characteristics
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• Signal detection problem – signal present or
signal not present
• Dim flash of light or radar signal (external signal)
• Corresponding detector signal (internal signal)
• Assume two normal distributions
• One when there is no external signal
• One when there is an external signal
• Assume variance is identical for both (see figure)
Pattern Classification, Chapter 2 (Part 3)
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Pattern Classification, Chapter 2 (Part 3)
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• The detector employs a threshold value to determine
whether the external signal is present or not
• We define a measure of discriminability that
describes the inherent properties of the signaland
noise but not the decision strategy – choice of
threshold
Pattern Classification, Chapter 2 (Part 3)
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Pattern Classification, Chapter 2 (Part 3)
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Pattern Classification, Chapter 2 (Part 3)
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Pattern Classification, Chapter 2 (Part 3)
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Pattern Classification, Chapter 2 (Part 3)