Hello .This problem has been troubled me for over a month.
Here's the actual problem :there are lots of products, each of them has an ID. Each of them is tested several times,or just once.
I want to compare data from row "TEST RESULT" of the same ID to evaluate stability of the test machine.
But now I am having trouble finding the ID that was tested at least 2 times .
Even after that,I am not sure how to compare their test results. Maybe avg(first-time-result minus second-time-result) through days or hours?
I really need some advice, thank you .
Retrieving data ...