An uncertainty budget needs compatible component definitions. Read the certificate’s uncertainty label and factor before entering the number.
Read the certificate fields together
Expanded uncertainty is obtained by multiplying a combined standard uncertainty by a coverage factor. If the certificate reports U and k, the corresponding standard value is U divided by k. A number without its label and factor cannot safely be treated as a standard component.
One invented conversion
Suppose a reference certificate states expanded uncertainty U=0.60 g with k=2. The standard component represented by that statement is 0.30 g. Entering 0.60 g as a standard component and later multiplying the budget by a coverage factor would expand that contribution twice.
Conversely, if the certificate already reports standard uncertainty, dividing by two merely because a spreadsheet expects it would reduce the stated contribution without justification. The invented values establish no permissible uncertainty for a filling trial.
Retain the original statement
Record U, k, units, coverage information and the applicable reference value together. Identify any other certificate conditions that affect use. Have the uncertainty reviewer confirm the component conversion before combining it with locally evaluated contributions.
Primary references: JCGM international vocabulary, JCGM international vocabulary, NIST measurement handbook.
Measurement review worksheet
This blank worksheet is for your own project. It contains no H M machine trial result.
| Question | Evidence to retain |
|---|---|
| Which uncertainty is reported? | Standard or expanded |
| What is the stated factor? | Certificate k and coverage notes |
| Where is the conversion recorded? | U/k with units |
Customer Questions
Should every certificate value be divided by two?
No. Use its actual uncertainty definition and factor.
Does k=2 always mean exactly 95%?
No. The applicable coverage interpretation must be retained.
Can units be omitted in the budget?
No. They are necessary for consistent calculation.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
Discuss Your Machine Requirement
Share your product, container, required output and the evidence needed for your technical review.
Request a Technical Review