Data collection errors can occur when data sources, methods, or instruments are inappropriate, inaccurate, or inconsistent. For instance, unreliable or outdated data sources may be used, a biased or unrepresentative sample may be selected, a poorly designed survey or interview may be applied, or the data may be recorded or transcribed incorrectly. To avoid or reduce data collection errors, it is important to set clear data needs and sources that align with evaluation questions and indicators. Additionally, a suitable data collection method should be chosen that matches the data type, population, and context. Furthermore, data collection instruments should be designed and tested to guarantee they are valid, reliable, and user-friendly. Likewise, data collectors should be trained and supervised to ensure they follow the same protocols and standards. Finally, the data should be checked and verified for completeness, accuracy, and consistency.