Activity Rating in Industrial Time Study

Introduction

Activity is a central concept in industrial time study and scientific work measurement. It is defined as the pace of execution of productive tasks and the degree of compliance with three fundamental factors:

• Fidelity to prescribed work methods

• Precision and coordination in movements

• Speed of execution of these movements

Consistency in performance over time is also a determining factor.

In this article, we will analyze in depth the rating of activity in the context of industrial time study: its importance, measurement methods, factors that affect it, and practical recommendations to improve the objectivity of assessments.

The objective is to provide the specialized reader with a complete and updated guide on this crucial aspect of work measurement engineering.

Importance of Activity in Time Study

Activity has a direct impact on the execution times of productive tasks. Higher activity translates into shorter observed times.

Before recording any time, it is absolutely essential that the analyst carefully assesses the level of activity displayed by the worker and not after the fact, so that their judgment is not biased by the results obtained.

This allows normalizing the observed times, eliminating individual and circumstantial variations, in order to obtain data representative of the actual work content of each task.

Without activity rating, the observed times would lack scientific validity, as they would only reflect the individual performance of the worker, and not the inherent content of the task itself.

Let’s look at a numerical example of this concept:

Operator A:

• Rated activity: 80%
• Observed time in task: 10 minutes

Operator B:

• Rated activity: 60%
• Observed time in same task: 13.3 minutes

If activity had not been rated, both times would seem equally valid to represent that task.

But when normalizing the times according to a standard activity of 100%, we obtain:

• Normalized time A: 10 * 0.80 = 8 minutes

• Normalized time B: 13.3 * 0.60 = 8 minutes

It becomes evident that the time inherent to the task is LESS than 10 minutes. Without activity rating, this fundamental data could not have been determined.

Activity Measurement Methods

Activity is measured by comparison against pre-established activity patterns or scales. The scales most commonly used in industrial practice are:

• Centesimal scale: defines levels of normal activity (100) and optimal activity (133).

• Bedaux scale: defines levels of normal activity (60) and optimal activity (80).

• BSI scales: defines levels of normal activity (75) and optimal activity (100).

• MTM: defines levels of normal activity (90) and optimal activity (120).

The analyst, based on their expertise, carefully observes the worker, compares their performance against these patterns, and finally issues a technical but inevitably subjective judgment. This assessment is known as “activity rating” or “activity judgment.”

Normal Activity

It corresponds to a constant, determined worker, without rush, like a worker not paid by piece rate, but well directed and supervised; seems slow but does not deliberately waste time while being observed. Walking speed comparable to 4.5 km/h.

Optimal Activity

It corresponds to an active, capable worker, like a skilled average worker paid by piece rate. Achieves the required level of quality and precision with tranquility. Walking speed comparable to 6.4 km/h.

Source: Adaptation of a table published by the Engineering & Allied Employers (West of England) Association, Department of Work Study.

Let’s look at an example of application on the centesimal scale:

• Null activity: 0

• Notoriously slow and unmotivated worker: 60

• Average or normal worker: 100

• Active and motivated worker: 133

On this basis, the analyst would observe the operator, analyze the speed and precision of their movements, their adherence to the method, and their consistency; and finally assign them a score within the chosen scale, according to their technical criteria.

Factors that Influence Activity

The main factors that modulate the level of activity exhibited by a worker are:

• Movement speed: higher speed, higher activity.

• Precision and coordination: harmonic and precise movements reflect greater mastery of the task.

• Method compliance: if the prescribed method is not followed, activity is affected.

• Consistency: activity must be maintained over time.

Other factors that also influence activity:

• Incentives: a worker under production-based remuneration systems will regularly exhibit higher activity.

• Fatigue: activity declines as the workday progresses and physical and mental fatigue accumulates.

• Experience: more expert and trained operators show higher activity in complex tasks.

Let’s analyze some representative examples:

• A novice operator, with dubitative and imprecise movements, will have an activity rated as low.

• A worker under monetary incentives will predictably have higher execution speed and consistency over time. Their activity will be consistently high.

• At the end of an exhausting day, fatigue will logically cause slower and less coordinated movements. The rated activity will have noticeably declined.

In all cases, the analyst must simultaneously consider the set of factors to integrate them into a balanced and precise assessment.

Practical Recommendations to Improve Objectivity

In order to achieve technically valid and objective activity ratings, the following practical recommendations are suggested for analysts:

• Previously study in depth the prescribed work methods for each task. Have them clear before starting observations.

• Meticulously and actively observe the worker’s movements and their dynamic characteristics. Detect possible improvements.

• Compare in parallel against predetermined visual patterns and videos to calibrate perception.

• Comprehensively consider all contextual factors that may be impacting activity.

• Rate the activity immediately before recording each time. Never the other way around.

• Validate the ratings against the opinions of other experienced analysts to detect deviations.

• Periodically update patterns and scales in the face of changes in production processes. Maintain technical validity.

• Always maintain an objective, measured, and strictly technical attitude. Avoid personal biases.

A careful, calibrated, and technically competent rating of activity is crucial to obtain normalized, reliable observed times that are representative of the actual work content.

Although rating inevitably involves a subjective component, adequate training, experience, and professional vocation minimize the influence of individual distortions.

Application in Remuneration Systems

Times normalized from the careful rating of activity constitute the technical basis of performance-based remuneration systems.

In these variable salary schemes, the aim is to equitably reward workers according to their real contribution, reflected in their individual activity and productivity.

For the success of these systems, time analysts must be extremely rigorous and consistent in their activity ratings. This will allow avoiding arbitrary or unjustified salary differences between workers.

Some useful guidelines for this purpose:

• Establish clear, precise, and updated standards of expected activity for each task.

• Regularly and thoroughly train analysts in the rating methodology. They must fully master the concepts and their practical application.

• Periodically validate a representative sample of studies. Detect and correct deviations in precision and criteria.

• Rotate analysts in studies of the same task to reduce systematic individual biases.

• Update activity patterns and scales if the technological conditions of task execution change. Maintain technical validity.

• Completely and summarily document each study. Make explicit and substantiate adopted assumptions.

A rigorous application of these guidelines will provide credibility, equity, and sustained adherence in variable performance-based remuneration systems.

Ethical and Legal Aspects

The determination of activity standards carries important ethical responsibilities for analysts:

• Do not falsify ratings to justify arbitrary cuts in remuneration.

• Do not yield to commercial pressures to artificially force standard activity.

• Comprehensively consider physical, cognitive, and emotional factors of workers, in addition to productivity.

• Always respect contractual agreements between the company and workers or unions.

• Communicate with full transparency and technical foundation any change in activity standards.

Likewise, activity measurements can have legal implications if used to support sanctions or dismissals. Maximum possible precision and objectivity are even more critical in those scenarios.

Consequently, solid technical training and impeccable professional ethics are indispensable for time analysts to perform their role with total responsibility.

Conclusions

The correct rating of activity is indispensable to obtain valid, equitable, and technically sustainable work measurements.

It requires expert observation, solid theoretical knowledge, and constant practical calibration through experience.

More than an exact science, activity rating constitutes a technical art that is progressively perfected with extensive and dedicated professional practice.

The concepts presented here seek to lay firm foundations for mastering this challenging but exciting aspect within the broad field of work and time measurement engineering.

The author trusts that this article will be useful for technicians, analysts, and specialists, and sincerely appreciates the reader’s interest. The author remains available to receive inquiries, comments, or contributions that enrich future articles on this transcendental subject.