Which day shows a violation of the R4s QC rule in the given chart?

To identify a violation of the R4s QC rule, it is essential to understand that this rule indicates that there should be no results outside the control limits within a set of replicate measurements. When analyzing the chart data, we are looking for four consecutive points that fall on one side of the average line, either above or below, or any instance where there are outliers beyond the control limits.

In this case, Day 15 shows a violation of the R4s QC rule because it displays four consecutive points that fall above the established control limits. This signal that the analytical measurements may be systematically biased and would require further investigation. Day 15’s data suggests a trend that warrants a review of the assay’s performance, as it breaches the guideline that aims to ensure the reliability and accuracy of the testing process.

In contrast, other days reviewed do not show a sustained pattern exceeding these limits and thus would not indicate a violation under the R4s QC rule.