What is data completeness in a monitoring network?

• A. The percentage of valid data in a period
• B. The total samples collected
• C. The maximum concentration observed
• D. The number of QA events

Answer: (A)

Data completeness is the percentage of valid data available during a defined monitoring period. It measures how much of the expected data actually reports as usable values, so a dataset with many missing or invalid readings has lower completeness even if a lot of samples were collected. For example, if you expect 24 hourly readings in a day and 22 are valid, completeness is about 92%. This differs from total samples collected, which counts quantity without judging validity; it also isn’t about the maximum concentration observed or the number of QA events, which relate to other aspects of data quality and monitoring but not how complete the data record is.