The meaning of "should"..?
Does "should" mean "obligation" in the sentence below?

Sentence:
Please specify the concentration of the positive control relative to the LoD of your test (note that ideally the positive control concentration should be such that it is close to the LoD of your test) and specify frequency of use.

I wonder if the positive control concentration does not have to be close to the LoD (close to LoD is ideal though). Or does that mean it is obligated to have the positive control concentration close to LoD (it is not acceptable if the positive concentration is not close to LoD)?

It would be a great help if you could guide me!
Many thanks in advance!

Question

The meaning of "should"..?
Does "should" mean "obligation" in the sentence below?

Sentence:
Please specify the concentration of the positive control relative to the LoD of your test (note that ideally the positive control concentration should be such that it is close to the LoD of your test) and specify frequency of use.

I wonder if the positive control concentration does not have to be close to the LoD (close to LoD is ideal though). Or does that mean it is obligated to have the positive control concentration close to LoD (it is not acceptable if the positive concentration is not close to LoD)?

It would be a great help if you could guide me!
Many thanks in advance!

Answer

Technically, I would say that 'should' is used here as a strong recommendation in the context of an 'ideal' outcome.  It's very close in meaning to an obligation because they would like the control concentration to be as similar as possible to the LoD of your test.  I wouldn't say that it's necessarily "unacceptable" for there to be a big difference, but if this is a graded exercise, you will score higher if the two substances closely match.

I hope this makes sense.  This is not my field of study.  I'm just explaining the English.

Answer

Thank you very much for your help! Hope you have a great day! :)