This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
The arithmetic in post #90 is right; the assumption feeding it is the part to check.
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.
I would not lead a decision with this, but I would not ignore it either.
Answering the question post #88 raises rather than the one it answers.
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.
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.
Right — I had this wrong and I am glad to have read it before it mattered.
Adding a null result on mass-error checker. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are.
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.
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.
Nothing to add on the substance. Thank you for taking the question at face value.
Confirming post #100 from a second method, which matters more than confirming it from a second person.
Checked the mass-error checker claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
The honest answer on mass-error checker is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter.
Most people get the first two right and then argue about the fourth.
Post #104 is right about the mechanism and I think understates the practical bit.
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.
Coming back to post #106, because the follow-up matters more than the original answer.
Reporting rather than recommending, on mass-error checker. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
Reading rather than answering, but this is the post I would point somebody at.
Post #110 and I disagree about the size of the effect, not about the direction.
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.
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.
Same conclusion as the reply above, reached differently, which is mildly reassuring.
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.
That is what I would do. It may not be what is correct.
The question underneath mass-error checker is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
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.
That has held every time I have looked, which is not the same as always.
This is the answer, and the reason it is the answer is the more useful part.
Post #116 answers the question as asked. The question underneath it is different.
On mass-error checker: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.
Answering the mass-error checker question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.
Post #118 is the version of this I will quote in future. One addition.
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.
That is the version I use. It may not be the version that is correct.