Combination calculation

Combination calculations closely follow the guidelines laid out in USP <81>. You can adjust calculations to your needs by performing an optional outlier test, setting the confidence level, and selecting the logarithm base.

Note: You can run combination calculations once you have referenced assay documents. The results of combination calculations are added to and saved with the Combination of microbial assays document.

Combination calculation sequence

Figure 1. Basic calculation steps performed for the Combination of microbial assays document type
Tip: The Combination of microbial assays document type provides standard reports that let you output results in print and electronic form.

Basic combination calculation settings

Setting Navigation
Perform outlier test (optional) Content editor > Analysis > Perform outlier test

Lets you check for outliers among the potencies that the Combination of microbial assays document draws from your assay documents. If you activate this option, PLA 3.0 performs the outlier test prior to combination calculations.

Note: The outlier test is only performed for combination groups that contain three or more valid samples.

The outlier test closely follows the guidelines laid out in Appendix 2 of USP <81>.

Tip: The test is only run once and can therefore detect no more than one outlier.
Confidence level (%) Content editor > Analysis > Confidence level (%)

Lets you set the confidence level to be used to determine the confidence interval that is calculated from the mean of the potencies from your assays and their standard deviation.

Logarithm base Content editor > Analysis > Logarithm base

PLA 3.0 performs combination calculations with logarithmized values. This option lets you select the logarithm base to be used.