Small correction to my own earlier position on mass-error checker. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
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Data & Tools · Calculators · continued
Second pass at: 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 · go to the accepted answer.
plateau_notes, post #4: No notes. Posting so the count is not one. Go to post
This follows post #31 rather than contradicting it.
Worth separating mass-error checker as a question about the compound from mass-error checker as a question about the documentation. They get answered by different people and only one of them is answerable here.
Collapsed as off-topic by two members at trust level 3 or above
Coming back to post #31, because the follow-up matters more than the original answer.
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.
That holds under the stated conditions and I have stated them.
The confident answers on mass-error checker and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
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a.nascimento, post #9: 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. Go to post
Adding a data point of agreement rather than a data point.
h.ramos, post #1: Posting this under the heading it deserves: Second pass at: The mass-error checker and its intended scope Everything below is what sits behind that. Posting a small dataset on mass-error checker. It is mine, it is uncontrolled, and the method is stated so it can be discounted appropriately. What I would like is not agreement but a… Go to post
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
I had written a reply contradicting post #36 and deleted it. Here is what survived.
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.
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Confirming post #36 from a second method, which matters more than confirming it from a second person.
I keep a log for mass-error checker specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.
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buffer_sheet, post #22: Mass-error checker came up in a thread eighteen months ago and was answered well. I cannot find it, which is itself the problem, so here is the reconstruction. Go to post
Post #36 describes the usual case. This is about the unusual one.
For anyone finding this later: the short answer on mass-error checker is that it depends on one thing, and the rest of the thread is people identifying which thing.
Ziegler, post #14: Post #13 answers the question as asked. The question underneath it is different. The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives. The claim is narrower than it sounds, and deliberately so. 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 modest claim, modestly supported.
On post #38 — agreed on the reasoning, with one qualification.
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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p.diallo, post #23: Thank you for the correction. I would rather find out here than later. Go to post
Where the mass-error checker reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.
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.
Happy to expand any of that if it is the useful part.
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Mass-error checker would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
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Collapsed as off-topic by two members at trust level 3 or above
Post #42 describes the usual case. This is about the unusual one.
A note on scope: what I am saying about mass-error checker applies to the case in the first post and I would not extend it further without checking.
gradient_file, post #20: Adding a null result on mass-error checker. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are. Go to post
Tools that run entirely in the browser send nothing anywhere, which matters more to some people here than others and is worth stating either way.
KStephanopoulos, post #31: Small correction to my own earlier position on mass-error checker. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely. Go to post
What I would tell a new member reading about mass-error checker for the first time: the confident posts are not the reliable ones, and the reliable ones are longer.
Clear enough that I do not think I have a follow-up, which is unusual.
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m.oyelaran, post #38: Confirming post #36 from a second method, which matters more than confirming it from a second person. I keep a log for mass-error checker specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it. Go to post
Filing a mild objection to the consensus on mass-error checker. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit.
Narrowing post #52, because the general version has more than one answer.
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.
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Post #54 put the caveat in the right place and I want to underline it.
A saved calculation is worth more than a remembered one. Write down the inputs alongside the result, because the result alone is unverifiable a month later.
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On mass-error checker, 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.
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p.diallo, post #23: Thank you for the correction. I would rather find out here than later. Go to post
One caution on mass-error checker: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
The arithmetic in post #57 is right; the assumption feeding it is the part to check.
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.
Where I would look next, rather than where I would stop.
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baseline_drift, post #44: 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. Happy to expand any of that if it is the useful part. Go to post
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.
It is the kind of thing that is obvious once and never again.
KStephanopoulos, post #31: Small correction to my own earlier position on mass-error checker. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely. Go to post
Picking up post #57: 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.