Rounding of figures in analytical results

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Rounding of figure is a mathematical method in which replacing of one number by another number to get the approximate and nearby value.

Rounding of figure is important because it gives the final reporting results as accurate and in easier form.

Rounding of figures can be done for both rounding of decimals (e.g. 10.7695 rounded to 100.766) and rounding of whole number (3350 rounded to 3300). 

Mostly in pharma industry the final results are calculated either manually or by using validated excel sheets or validated calculators which are prepared in a automated way give the final results in rounding figures.

Significant figures:

These figures are used to express precision or any uncertainty associated with reported numerical result.

All non-zero digits are significant (e.g. 1256 having 4 significant figure)

All zero between non-zero digits are significant (e.g. 205.13004 having 8 significant figure)

Starting zero in a numerical value is not significant (e.g. 0.00054 having 2 significant figure)

Last zero in a numerical value counts for significant figure (e.g. 12.2100 having 6 significant figure)

Rounding of figures method

When rounding of is required, consider only one digit in the decimal place to the right of last place in the limit expression. If this digit is smaller than 5 it is eliminated and keep the presiding digit is unchanged. If this digit is greater than 5, it is to be eliminated and increase the preceding digit by one. If this digit is equals to 5, eliminate the 5 and increase the preceding limit by one.

Some examples are given below in a table:

Sr. No. Standard requirements original value Rounded value Complies or not complies
1 Assay limit  > 98.0% 97.96%  98.0% Yes
97.92%  97.9% No
97.95%  98.0% Yes
2 Assay limit  < 101.5% 101.55% 101.6% No
101.46% 101.5% Yes
101.45% 101.5% Yes
3 Limit test < 0.02% 0.025% 0.03% No
0.015% 0.02% Yes
0.027% 0.03% No
4 Limit test < 3 ppm(0.0003%) 0.00035% 0.0004% No
0.00025% 0.0003% Yes
0.00028% 0.0003% Yes

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