Calculadora de Prueba Chi-Cuadrado — Fórmula
## How to Perform a Chi-Square Test
### Formula
**chi-square = Sum of [(Oi - Ei)^2 / Ei]**
Compare the computed chi-square statistic to the chi-square distribution with k-1 degrees of freedom (where k is the number of categories). If the statistic exceeds the critical value, reject the null hypothesis that the observed distribution matches the expected distribution.
### Formula
**chi-square = Sum of [(Oi - Ei)^2 / Ei]**
Compare the computed chi-square statistic to the chi-square distribution with k-1 degrees of freedom (where k is the number of categories). If the statistic exceeds the critical value, reject the null hypothesis that the observed distribution matches the expected distribution.
Ejemplo Resuelto
Four categories: observed 45, 35, 25, 45; expected 40, 40, 30, 40.
- c1 = (45-40)^2/40 = 25/40 = 0.625
- c2 = (35-40)^2/40 = 25/40 = 0.625
- c3 = (25-30)^2/30 = 25/30 = 0.8333
- c4 = (45-40)^2/40 = 25/40 = 0.625
- Chi-square = 0.625 + 0.625 + 0.8333 + 0.625 = 2.7083
- df = 4 - 1 = 3
- Critical value at alpha=0.05, df=3 is 7.815
- Since 2.7083 < 7.815, do not reject H0