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CONFIRMATION BIAS

CONFIRMATION BIAS. Confirmation Bias: A Ubiquitous Phenomenon in Many Guises Raymond Nicholson, TUFTS Review of General Psychology 50+ pages non-technical 7 full pages of references Francis Bacon (1620) “…great and pernicious predetermination…” Poyla (1954)

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CONFIRMATION BIAS

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  1. CONFIRMATION BIAS

  2. Confirmation Bias: A Ubiquitous Phenomenon in Many Guises • Raymond Nicholson, TUFTS • Review of General Psychology • 50+ pages • non-technical • 7 full pages of references • Francis Bacon (1620) • “…great and pernicious predetermination…” • Poyla (1954) • “…scientific thought as distinguished from everyday thought.”

  3. BIAS Building a Case **no expectation of impartiality Treatment and Evaluation of Evidence Motivated Bias Philosophy Logic Statistics Psychology Impartial Evaluation Unmotivated Bias Hempel (1945) Observed: A white shoe Concluded: All ravens are black. Logic: All observed non-black things are non-ravens (the Contrapositive) Silly? All these insurgents are Muslim…

  4. Incarnations of Confirmation Bias • Evidence interpretation • Evidence censoring • Restriction of alternative hypotheses • Seeking confirmatory evidence • Reification – over-estimating the salience of a taxonomy • Illusory Correlation • Primacy – becoming biased by the beginning of a stream of evidence, early hypothesis building

  5. Wasson(1966) • Four cards presented. Cards have a number on one side and a letter on the other. • Confirm or deny: All vowels have even numbers on the other side. A B 4 7 • Most subjects (~90%) flip “A” and/or “4” • People seek to confirm the hypothesis, they do not seek countervailing evidence.

  6. Taylor and Smyth (1860’s) • Egyptologists and Numerologists, they discover “too strange” relationships in Pyramid dimensions. • (2 x base)/height = p • base/casing stone = 365 • height * 109 = distance from earth to sun • density of the earth • period of the procession of the earth’s axis • mean temp of the earth’s surface • Conclusion: Space aliens directed the construction of the Pyramids

  7. Einstein and the Expanding Universe • Universe assumed static until mid-50’s • Expanding universe model could have been discovered by any post-Newton astronomer (S. Hawking, 1988) • Einstein actually had evidence of expansion as a by-product of General Relativity, but covered it with his now-infamous Cosmological Constant. • Called this the biggest mistake of his career.

  8. Type 1 Error • recall P[type 1] = P[reject Ho|Ho] = a • Typical 1-tailed test runs on a = 0.025 • In 40 independent tests, you EXPECT one false rejection • Sequential testing is a great temptation in simulation analysis • Ability to make STDERR arbitrarily small means that meaningful indifference zone needs to be determined a priori.

  9. Confirmation Bias • Our leaders and customers have it • Our families and neighbors have it • We have it, but we can protect ourselves

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