What is the Chi-square formula and what do its components represent?

The image displays the Chi-square formula.

The Chi-square formula is given as:

$$X^2 = \frac{(o-e)^2}{e}$$

Where:

• $X^2$ is the Chi-square statistic.
• $o$ represents the observed frequency.
• $e$ represents the expected frequency.

This formula calculates the contribution of a single category to the overall Chi-square statistic. For a complete Chi-square test, these values are summed across all categories.