Characteristics of a Scientific Experiment
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
4. Failure to use sample size information
5. Tendency to explain chance events
6. Gambler’s fallacy
7. Conjunction fallacy
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
Statistical summaries of relevant information is less effective in changing opinion than one face-to-face opinion, e.g., Hamil, Wilson & Nesbett (1980) prison guard exp., media
Students choosing courses?
Vietnam - weekly fatality statistics (200-300), Life magazine
The anecdotes used in media (politicians etc.)
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
e.g., Bayes theorem
Bayes Theorem
Assuming there is no reason for one taxi colour to have been in an accident than the other:
base rate probability of the taxi being blue =.15
she would identify it as such 80% of the time: .8*.15=.12
base rate probability of the taxi being green =.85
she would erroneously identify it as blue 20% of the time: .2*.85=.17
proportion of taxies identified as blue that actually were= .12/(.12+.17)=.41
Bayes Theorem
Bayes Theorem
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
Handout
Framing
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
4. Failure to use sample size information
Sample Size
In which would you expect to have more days during which over 60% of the babies born are female?
A) Large hospital? or
B) Small hospital?
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
4. Failure to use sample size information
5. Tendency to explain chance events
stock market analysis
illusions of control (lottery tickets - picking numbers, books etc.)
personal coincidences
Tendency to explain chance events
Wouldn’t it be, like, really weird karma if, like, two people in this class had the same birthday?
Bet that two people in this class were born on the same day of the year (not necessarily the same year)?
In group of 23, chances are 50:50
Coincidences do not need explanation
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
4. Failure to use sample size information
5. Tendency to explain chance events
6. Gambler’s fallacy
Linda
Linda
Difficulties with Probabilistic Reasoning
(from Stanovich: How to think straight about psychology)
1. Salience of atypical cases ("man-who statistics")
2. Insufficient use of probabilistic information
3. Cognitive illusions
4. Failure to use sample size information
5. Tendency to explain chance events
6. Gambler’s fallacy
7. Conjunction fallacy
(Linda - representative heuristic)
Stanovich
While many scientists sincerely wish to make scientific knowledge accessible to the general public, it is intellectually irresponsible to suggest that a deep understanding of a particular subject can be obtained by the layperson when that understanding is crucially dependent on certain technical information that is only available through formal study.
Such is the case with statistics and psychology.
Innumeracy (John Allen Paulos)
Inferential Statistics (Ch. 12)
Parametric Statistics
Nonparametric Statistics
Hypothesis Testing
Hypothesis Testing
Hypothesis Testing
Inferential Statistics
Factors Contributing to Group Mean Differences
Factors Contributing to Within-Group Differences
What Can You Do?