How are data completeness and data availability differentiated in ambient monitoring data management?

• A. Completeness is the proportion of valid data collected.
• B. Completeness is the proportion of valid data collected; availability refers to the possibility to collect data given operational conditions and site status.
• C. Completeness and availability are the same concept.
• D. Availability is the proportion of valid data collected.

Answer: (B)

The key idea is that data completeness and data availability measure different things in ambient monitoring. Completeness is about the data you actually collected that meet quality standards—the fraction of measurements that are valid and usable. It tells you how much of the collected data is reliable.

Availability, on the other hand, is about whether data could have been collected at all during the monitoring period. It accounts for uptime and operational conditions—instrument health, power, communications, site status, and any outages or maintenance. It answers whether data collection was even possible, not whether the collected data were valid.

For example, if a monitor runs continuously but many measurements fail QC, completeness declines because fewer data points are valid. If the instrument is offline for a period, availability declines because there were fewer opportunities to collect data, even if the data produced during online times are all valid. Thus, completeness corresponds to the proportion of valid data collected, while availability refers to the possibility to collect data given operational conditions and site status.