Validating a calculator against hand arithmetic — what changed since posts 91–120
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
Picking up post #89: that is the part I would want checked first.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.
Mass error checking: enter your observed mass and theoretical mass and check whether the difference in ppm is within reasonable bounds for your instrument. Useful sanity check on LC-MS results.
Not the whole picture, but the part of it I can speak to.
This follows post #93 rather than contradicting it.
Do the arithmetic by hand the first few times, whatever tool you use afterwards. A calculator with a wrong input gives a confident wrong answer and there is nothing in the interface to tell you.
The most useful reply I ever got about Validating a calculator against hand was a request to state my units. It sounds like pedantry and it has saved me twice.
Reporting rather than recommending, on Validating a calculator against hand. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
Unit-conversion tools are only as good as the assumption they make about the syringe. Ask what barrel and what graduation interval it assumed before trusting the units figure.
The part I am sure of is shorter than the part I have written.
Collapsed as off-topic by two members at trust level 3 or above
Everything in post #101 holds. The case it does not cover is the one I have.
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
Fine by me. I had wanted a stronger conclusion and there is not one available.
Where a calculator and your own arithmetic disagree, the productive move is to find which step differs rather than to decide which is right.
Speaking for myself and not for anyone else who has posted here.
The calculators maintained on this site are open-source and verifiable. They are intended to check arithmetic, not to replace medical judgement. Using them is optional and they are provided for convenience.
It took me longer than it should have to see that.
Answering the question post #105 raises rather than the one it answers.
Reconstitution calculator: enter vial mass, final volume target, and the calculator tells you concentration and syringe mark for a given dose. Useful for double-checking arithmetic when you are doing it by hand.
I would call the community position on Validating a calculator against hand likely rather than established, and I would be comfortable defending that hedge.
Noted, and thank you for writing it out rather than summarising it.
Confirming post #108 from a second method, which matters more than confirming it from a second person.
Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.
This follows post #108 rather than contradicting it.
Why calculators are not medical advice: they do arithmetic. Medical decisions are not arithmetic. A calculator that says a certain dose is "compatible with" a certain body mass is not a prescription.
The literature is thinner on this than the confidence in the thread implies.
Worth separating two things that post #110 runs together.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
Second this, and I would have said it less carefully.
Taking post #112 at face value and following it one step further.
Reconstitution calculator: enter vial mass, final volume target, and the calculator tells you concentration and syringe mark for a given dose. Useful for double-checking arithmetic when you are doing it by hand.
Reading this Validating a calculator against hand thread as someone who came in with a fixed view: the third and seventh replies moved me and the confident ones did not.
On Validating a calculator against hand, I would rather understate and be corrected upward than overstate and be quoted. That is a house style here and it is a good one.
Everything in post #115 holds. The case it does not cover is the one I have.
Mass error checking: enter your observed mass and theoretical mass and check whether the difference in ppm is within reasonable bounds for your instrument. Useful sanity check on LC-MS results.
If this contradicts something upthread, the upthread version may well be the better one.
Validating a calculator against hand has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.
Precision and significant figures: the calculators do not round to match your input precision. If you input values to one decimal place, the output might have more. Use significant figures appropriate to your input precision.
Written quickly, so the reasoning may be tighter than the wording.