Adding a reference point for mass-error checker. Mine is a single case, collected without controls, and I am posting the method alongside it so it can be discounted appropriately.
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Data & Tools · Calculators · continued
The mass-error checker and its intended scope posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
h.ramos, post #16: Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription. A partial answer, offered because a partial answer beats none. Go to post
I had written a reply contradicting post #31 and deleted it. Here is what survived.
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.
That is a description of practice, not a recommendation of it.
Picking up post #32: that is the part I would want checked first.
The parts-per-million mass-error calculation is simple enough to do mentally to one significant figure, which is a good habit because it catches an order-of-magnitude slip immediately.
It is one reading of the data and not the only reasonable one.
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Genuine question rather than a rhetorical one: has anyone here actually observed mass-error checker, as opposed to read about it? The thread is long and I cannot tell.
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One more thing on mass-error checker that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
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f.fenwick, post #27: What would change my mind on mass-error checker is a second dataset collected by someone with no stake in the first. Until then I hold it loosely and I would rather say so than pretend to more. Go to post
This follows post #35 rather than contradicting it.
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 from notes rather than memory, which is why the numbers are specific.
Post #37 answers the question as asked. The question underneath it is different.
The most useful reply I ever got about mass-error checker was a request to state my units. It sounds like pedantry and it has saved me twice.
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Mass-error checker has been discussed here with more heat than it deserves, mostly because two definitions have been in play the whole time.
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t.ibarra, post #32: I had written a reply contradicting post #31 and deleted it. Here is what survived. 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. That is a description of practice, not a recommendation of it. Go to post
I had read the opposite somewhere and cannot now find where, which tells me something.
r.villalobos, post #23: Practical note on mass-error checker: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow. Go to post
Adding the measurement that post #42 says would settle it.
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.
Two claims get bundled together under mass-error checker and they need separating. The descriptive one — this is what was observed — is usually well supported. The causal one — this is why — usually is not.
Almost every disagreement in threads like this one dissolves once you say which of the two you are making.
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cannula_trace, post #39: Post #37 answers the question as asked. The question underneath it is different. The most useful reply I ever got about mass-error checker was a request to state my units. It sounds like pedantry and it has saved me twice. Go to post
Answering the question post #44 raises rather than the one it answers.
I changed my mind about mass-error checker after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens.
s.bruun, post #20: Where I part company with post #16, and it is a narrow parting. 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. Adding it in case it saves somebody the… Go to post
Adding the boring version of mass-error checker, because the interesting version keeps getting posted and the boring one is usually right.
Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.
Post #47 is right about the mechanism and I think understates the practical bit.
Where I have landed on mass-error checker, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.
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ar.petrov, post #28: Picking up post #25: that is the part I would want checked first. 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. Noting that the question and the thing people usually mean by it are different. Go to post
Post #48 and I disagree about the size of the effect, not about the direction.
Whatever the answer on mass-error checker turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction.
da.bakker, post #40: A calculator that shows its working is worth ten that give an answer. The whole value is being able to see which step you disagree with. Go to post
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.
A calculator that shows its working is worth ten that give an answer. The whole value is being able to see which step you disagree with.
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Building on post #54 rather than restating it.
I have been on both sides of the mass-error checker argument in this category within eighteen months, which should tell you how strong the evidence for either side is.
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t.varga, post #49: Adding the boring version of mass-error checker, because the interesting version keeps getting posted and the boring one is usually right. Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does. Go to post
Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription.
Everything in post #56 holds. The case it does not cover is the one I have.
What I want from this mass-error checker thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.
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