Current Slide

• Χ^2 (chi-square) test

\[ X^{2}=\sum \frac{(Observed-Expected)^2}{Expected} \]

• The larger the Χ^2 value, the more likely the variables are related
• The cells that contribute the most to the Χ2 value are those whose actual count is very different from the expected count
• Correlation does not imply causality
• # of hospitals and # of car-theft in a city are correlated
• Both are causally linked to the third variable: population