- Data Quality: Inaccurate or incomplete data can lead to misleading results. - Complexity: Some techniques require a good understanding of statistical methods. - External Factors: Unpredictable events (e.g., economic changes, competitor actions) can impact your results and are hard to factor into your analysis. - Overfitting: Making your model too complex can result in overfitting, where it performs well on historical data but poorly on future data.