Overall %RSD for intermediate precision

If you have two sets of precision test data, one from analyst 1-day1, and another one from analyst 2-day2, how exactly do you calculate the overall % RSD for both tests?

Analyst1 Analyst 2

Results 1 Results 2

mean 1 mean 2

sd 1 sd 2

%RSD 1 % RSD 2

What is the correct way to calculate overall % RSD?


Dear almin,

As per USP and ICH guidelines Precision will perform

  1. Repeatability: (1st set) calculate the Mean, SD and % RSD for the same (six replicates)
  2. Intermediate precision: (2nd set) calculate the Mean, SD and % RSD for the same ( six replicates) and also Overall Mean , SD and % RSD for the two sets (twelve replicates).
    For intermediate precision case we have to check % RSD of six replicates and Overall % RSD of Twelve replicates of Repeatability and Int. precision separely.

For Japan market: Int. Precision study is different for the USP. i.e. six sets required. for details see attachment.


guidance_004_analytical_test_method_validation_-_precision_and_accuracy_sample.pdf (117.6 KB)