In this post, I want to talk about the proper way to express test results on certificates of analysis. To explain this, I am going to talk about the concept of significant figures (or significant digits). What are significant figures?
According to Wikipedia:
“The significant figures of a number are digits that carry meaning contributing to its measurement resolution.”
If you are unaware, there are two sets of test methods that are currently in use for many of the common tests that we see reported on data sheets and certificates of analysis. This has caused a lot of confusion.
To add to the confusion, I have seen many data sheets and certificates of analysis in which data is reported incorrectly. None more than izod impact. There is currently an ASTM method and an ISO method for testing izod impact. Although some data sheets claim that they are, the two test methods used for izod impact are definitely not equivalent. They are two different test methods and there is no way of converting between the two.