To calculate split half reliability, the test is divided into two equal halves, either randomly or systematically. The scores from both halves are then correlated using statistical methods, such as the Pearson correlation coefficient. The formula used is:
\[ \text{Spearman-Brown Prophecy Formula} = \frac{2 \times \text{correlation of halves}}{1 + \text{correlation of halves}} \]
This formula adjusts the correlation to estimate the reliability of the full test based on the split halves.
