the.com/correlation
two things holding hands while everyone assumes one shoved the other
means a statistical relationship in which two things tend to vary together, so that knowing one tells you something about the other — without implying that either causes the other
from From Latin 'com-' (together) plus 'relatio' (a carrying back, a relation), itself from 'referre,' to carry back or report. It surfaced in English scholarly Latin as 'correlatio,' meaning a mutual relation, and by the 19th century the statistician Francis Galton and his protégé Karl Pearson gave it its precise numerical sense — the degree to which two measured things move in step.
- causation myth
- correlation never proves one thing caused another
- spurious links
- cheese consumption tracks deaths by bedsheet tangling
- the range
- measured from -1 to +1, zero means nothing
- hidden third
- a lurking variable often pulls both strings
- coined 1888
- Francis Galton formalized it studying heredity
smoking and lung cancer — r=0.73 correlation established in framingham heart study and replicated globally
education level and income — 0.65-0.80 correlation coefficient in us census bureau data