Answer: Proportion of variance in Y explained by X.
- A The correlation coefficient itself, without squaring it
- B Proportion of variance in Y explained by X
- C The slope of the fitted regression line
- D The raw sum of squared residuals from the regression
Correct answer: B. Proportion of variance in Y explained by X
Explanation: SS_total = Σ(yᵢ−ȳ)², SS_residual = Σ(yᵢ−ŷᵢ)². R² = 1 − SS_residual/SS_total = SS_regression/SS_total. R² ∈ [0,1]; a value of 0.85 means 85% of variance in Y is explained by the regression model.
In a perfectly normal (bell-shaped) distribution, mean, median, and mode all coincide at the centre; about 68% of data falls within 1 standard deviation of the mean, 95% within 2, and 99.7% within 3 - the empirical rule used to judge how typical or extreme a value is.
Concept context
Mean, median, mode, standard deviation, and data interpretation