- Is price an indication of quality (in chocolate cakes)?
- Correlation coefficient (r):
- definition and visual presentation
- Example of twins:
- two brothers(twins) separated at birth
- environment vs heredity: judging influence of family environments by comparing
correlations of twins at home and twins separated
- correlation of twins' intelligence same for separated/non separated
- computation of r
- Reasons why r is between -1 and 1, why it is + or -, and why it is unitless
- Live ball controversy (baseball): Are there too many Home Runs?
- people looking at HRs, not strikeouts.
- predicting salaries from HR totals
-least squares method of prediction
-r in describing percentage of variation (usefulness of regression)
- Survey of equal opportunities in education (1960s) Coleman report
- small r in test scores vs school improvement
- turned attention to type of schools where scores were good, i.e.
not improvement of schools, but characteristics of good schools
(Mosteller)
- Correlation doesn't mean causation!
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