Assistant Statistical Officer Paper II · 9 Correlation · APPSC Paper I
9.1 Correlation notes
2 notes, in reading order.
- 9.1.1Correlation: types, scatter diagram and Karl Pearson's coefficient
Correlation measures how closely two variables move together in a straight-line pattern; Karl Pearson's coefficient r = Cov(x, y) ÷ (σx σy) gives this as a pure number between −1 and +1.
Advanced · 9 min · Read here - 9.1.2Spearman's rank correlation (with tied ranks) and probable error
Spearman's rank correlation R = 1 − 6Σd² ÷ n(n² − 1) measures agreement between two rankings; the probable error 0.6745 (1 − r²)/√n tells whether a sample r is large enough to be taken seriously.
Advanced · 7 min · Read here
Practise Correlation. Questions with answers explained, from the same topics.
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