What must be included in calculations for the next month's QC limits?

The correct approach for calculations of the next month's quality control (QC) limits is to include data that falls within the range of ±2 and ±3 standard deviations (s) from the mean. This range is essential because it allows for the assessment of both the typical variation in measurements and any potential outliers that may exist.

Including data within this range ensures that the limits are set based on a comprehensive understanding of the variation in the QC results. The ±2s range captures about 95% of the results in a normal distribution, which is critical for identifying control limits that reflect routine performance. By considering results from both ±2s and ±3s, the calculation becomes more robust, accommodating for possible fluctuations that may not represent system errors but are still part of the inherent variability of the assay.

The other options do not comprehensively represent the necessary data for establishing accurate QC limits. Focusing solely on ±2s may overlook important data points that could inform the behavior of the QC results, while only using results from the current week excludes valuable historical context necessary for a well-founded QC limit calculation. Aiming to utilize only previous QC results disregards the immediate and recent data that can impact the understanding of system performance. Thus, including data between