Contingency Tables (AQA A-Level Further Maths): Quizzes

$\frac{\text{row total} \times \text{column total}}{\text{grand total}}$

5

$X^2 = \sum \frac{(O_i - E_i)^2}{E_i}$

6

Only for $2 \times 2$ tables

$X^2$ is always positive or zero

There is no association between the variables

When any expected frequency is below 5

Reject $H_0$, evidence of association

Reduces the $X^2$ value slightly