From the chi-square value, sample size and degrees of freedom of a contingency table, compute Cramer's V to measure the association strength between two categorical variables.
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Pearson chi-square statistic | chi-square = sum (O - E)^2 / E | Pearson K. (1900), On the criterion that a given system of deviations... |
| Cramer's V | V = sqrt( chi-square / (n · min(r-1, c-1)) ) | Cramer H., Mathematical Methods of Statistics (1946), Princeton Univ. Press |
| Degrees of freedom | df = (r-1)(c-1), where r = rows and c = columns | Cramer H., Mathematical Methods of Statistics (1946) |
| Effect size benchmarks | 0.1 small / 0.3 medium / 0.5 large; for a 2x2 table V equals phi | Cohen J., Statistical Power Analysis for the Behavioral Sciences (1988) |
统计指标、置信区间与样本量的测算。