## Significant digits or not significant digits ... [General Statistics]

❝ … thats the question (*Hamlet*).

❝ But I have seen **almost always** constant decimal places (mostly 2-3) in the result from analysts.

Yes, it’s a pity.

❝ May be this is because they all use M$-EXCEL .

Agree, but even for them help is on the way.

In cell

`A1`

: original value (to 15 significant figures, if they like)In cell

`B1`

: `=IF(A1>1000,ROUND(A1/10,0)*10, IF(A1>100,ROUND(A1,0), IF(A1>10,ROUND(A1,1), IF(A1>1,ROUND(A1,2),ROUND(A1,3)))))`

Custom format of column

`B`

: `0.???`

… will handle values between 0.1 and 10000.

❝ Have you convinced your analysts in using significant digits?

Since I’ve worked as an analyst myself for quite a long time,

*mainly*I succeeded, because I speak the same language.

❝ Or is the discrepancy to the analytical report not an issue?

Yes it is. As a precaution I describe the procedure in the SAP – which is submitted to the EC and the competent authority beforehand. I never experienced any problems. But still I try to avoid such situations and talk to the analysts…

❝ ❝ For many analytical methods even rounding to *two* significant

❝ ❝ digits would be sufficient – but I would guess everybody would

❝ ❝ start screaming then …

❝ Thats a pity, but "The customer is king".

Yes, but I would say it’s also part of our job to do some education. Otherwise

**Rubbish in, rubbish out!**

❝ ❝ I do rounding of analytical data to three significant figures …

❝ Am I right in assuming that you use the rounded values for further processing (PK analysis)?

Exactly.

❝ What about 3 significant digits if LLOQ is given by the analyst with 2 decimals but only 2 significant digits (f.i. 0.88 nano/whatever)?

I can only use the data I get. Three significant figures actually are too high for many analytical methods anyway. If the LLOQ is given with 0.88 I keep it as it is.

As said in my previous post 0.88 implies everything between 0.875 and 0.884, or ~±0.5%, which is just ridiculous. I would prefer 0.9 (1 significant figure = ~±5%)

❝ ❝ C_{max}… three significant figures; AUC as an integrated

❝ ❝ parameter to four significant figures …

❝ AUC (roughly spoken summed conc. multiplied by time ...) gains precision in comparision to Cmax? I had expected the contrary.

If I look at AUC as an integrated function, most (if actual rather than scheduled sampling times are used – all) the error is contributed by the concentrations. I expected some kind of dampening effect – but to be honest I never checked it before. According to the propagation of errors the muliplication of two erroneous values leads to an addition of errors.

If we assume no error in sampling times,

**AUC should be given to the**.

*same degree of precision*as concentrationsI will modify my SOP, thanks!

❝ Again the question: Rounded values for further processing (statistical analysis of bioequivalence) ?

Yes.

*Dif-tor heh smusma*🖖🏼 Довге життя Україна!

_{}

Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮

Science Quotes

### Complete thread:

- Significant digits or decimal places d_labes 2008-03-26 13:15
- Significant digits (IMHO) Helmut 2008-03-26 16:12
- Significant digits or not significant digits ... d_labes 2008-03-27 10:10
- Significant digits or not significant digits ...Helmut 2008-03-27 20:43
- Significant digits or not significant digits ... d_labes 2008-03-28 11:00

- Significant digits or not significant digits ...Helmut 2008-03-27 20:43

- Significant digits or not significant digits ... d_labes 2008-03-27 10:10

- Significant digits (IMHO) Helmut 2008-03-26 16:12