Pace Rating Scales: ILO vs Bedaux
Interpret ILO and Bedaux rating scales, their reference performance levels and the limits of observational rating.
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Rating pace is not measuring utilization
Performance rating compares execution speed against a defined reference. The observed share of direct work is a different concept: activity or utilization under the study classification. That proportion can be estimated without pace rating; rating becomes relevant when normalizing manual time for a standard.
Do not apply the same judgment indiscriminately to manual action, an automatic cycle, and diagnostic work. Speed alone does not explain quality, physical effort, skill, or work value.
Scale versus appraisal method
A numerical scale and the method used to assign its values are separate choices. Appraisal can require training, comparable references, and consistency checks. Renaming a scale does not eliminate subjectivity or reactivity.
The IISE technical glossary distinguishes rating, factor, and scale, usually expressing normal performance as 100. ILO's Introduction to Work Study is a reference for the complete procedure, not certification of every observer's accuracy.
Percentage scales and Bedaux protocols
Under a percentage convention with normal reference 100, an assigned 110 corresponds to factor 110/100=1.10. For a system described as Bedaux, document the scale reference, work-unit definition, and treatment of rest before converting values.
Do not interpret work points as percentages or raw minutes without checking the convention. The Bedaux label alone does not establish which components are included or make rating more objective.
| Aspect | Required check in either system |
|---|---|
| Reference | Meaning of normal performance |
| Unit | Scale value, factor, or quantity of work |
| Time | Seconds or minutes and included content |
| Rest | Added separately or embedded in the definition |
| Repeatability | Observed disagreement on comparable work |
An example with explicit units
If a manual task takes nine observed minutes and the justified factor is 0.90, normal time is 9×0.90=8.1 normal minutes. Do not automatically label this “8.1 B”: that unit needs a further definition.
An assigned 90 on a scale with normal reference 100 gives factor 0.90. If another scale expresses the same level with different numbers, use assigned/reference value rather than the assigned number alone. Changing the scale does not physically change the work.
Select and verify
Check training, references, recording practicality, and consistency between analysts. No evidence is established here for a universal ±5% scale error, moderate Hawthorne effects in one scale versus high effects in another, or scientific or legal superiority.
Rating uncertainty cannot simply be added to a binomial margin or resolved through more state observations. Examine its sources separately and document their effect.
Application and limits
Normal time = observed time×factor where normalization is appropriate. Add allowances using an explicit denominator without double counting. No rating scale directly produces OEE: equipment performance needs ideal cycle time, counts, and run time; quality needs good-unit counts.
Do not attribute implementations of particular scales to an application without documentation. Before using a standard for planning or incentives, verify method, conditions, and the approval procedure.