Several factors can contribute to Type II errors in email marketing: 1. Insufficient Sample Size: Small sample sizes can lead to inconclusive results, making it harder to detect true differences between variants. 2. Poor Data Quality: Inaccurate or incomplete data can skew your analysis and lead to incorrect conclusions. 3. Incorrect Statistical Methods: Using inappropriate statistical tests or failing to account for variables can result in Type II errors. 4. Human Bias: Personal biases can influence how you interpret data, leading to false negatives.