Percentage difference between two areas?

My method states to "Compare the area of active in the Limit Solution to that of the area of active in the Detection Solution. The difference in the areas cannot be greater than 2%". 

How is this calculated? Is it a simple case of Area in Limit/Area in Detection*100 or do I need to go deeper to calculate the difference and use labels/custom fields such as:

ABS(((Limit.%.(Area)-Detection.%.Area))/((0.5(Limit.%.(Area)+Detection.%.(Area)))*100)


It doesn't say relative or absolute difference, it just says Difference. 

Answers

  • I think I have calculated % difference in a different manner at every company that I have worked for.

    The only comment I will make is your last equation above is an acceptable way to do this.

    Some companies for which I have worked use more of a % deviation from a calibration curve while others use more of a recovery.

    I think the important things here is to pick a method and stick with it.

    If this is a compendial method, then my recommendation would change to: email the SME for the monograph.

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