An Ontological Difference
It is common to confuse Work Sampling with the traditional Time Study. However, they are fundamentally different techniques in their approach, methodology and applications.
⏱️ Time Study
Continuous measurement of the duration of specific operations.
- • Stopwatch + direct observation
- • Measures how long each task takes
- • Output: Standard time per operation
- • Requires 100% cycle observation
📊 Work Sampling
Instantaneous observations at random moments.
- • Quick observation (snap reading)
- • Measures what proportion of time each activity occupies
- • Output: Percentage per category
- • Does not require continuous observation
Complete Comparison Table
| Characteristic | Time Study | Work Sampling |
|---|---|---|
| Type of data | Duration (seconds, minutes) | Frequency (% of time) |
| Observation | Continuous throughout the cycle | Instantaneous at random moments |
| Observer presence | Constant next to the worker | Momentary or remote |
| Hawthorne effect | High (intense observation) | Low (discreet observation) |
| Simultaneous subjects | 1 worker/machine | Multiple (entire cell) |
| Short cycles (<2 min) | ✅ Ideal | ❌ Not recommended |
| Varied activities | ❌ Hard to apply | ✅ Ideal |
| Allowances | Added to normal time | Measured directly |
| Cost per study | High (observer hours) | Lower (distributed observations) |
When to Use Each Technique?
Use Time Study when:
- You need the exact time of a work cycle
- The operation is repetitive and short (<5 minutes)
- You will establish standard times for incentives
- You can observe one station at a time
- The worker performs always the same task
Use Work Sampling when:
- You need to know what proportion of time is dedicated to each activity
- The tasks are varied and irregular
- You want to measure delays, waits or non-productive time
- You must observe multiple workers or machines
- You cannot be constantly present
- You want to determine real allowances (not theoretical ones)
💡 Choice example
Scenario: A manager wants to know why the production line is missing its targets.
If you suspect that:
"The worker is slow at the operation"
→ Time Study
If you suspect that:
"There are many interruptions and waits"
→ Work Sampling
Unique Advantages of Work Sampling
Less intrusive
The worker doesn't feel "watched" constantly, reducing the Hawthorne effect.
Multi-subject
A single observer can study an entire work cell simultaneously.
Time-flexible
Observations are spread over weeks, no full days of observation required.
Measures the invisible
Captures delays, waits and inefficiencies that traditional time study does not record.
Limitations of Generalist Software
"Time tracking" applications (Clockify, Toggl, Harvest) are designed for billing and payroll, not statistical sampling. They present structural limitations:
| Problem | Generalist Apps | Our App |
|---|---|---|
| Record type | Manual (Start/Stop) | Automatic random |
| Randomness | ❌ Not available | ✅ Built-in engine |
| Sample size (N) | ❌ Not available | ✅ Automatic |
| VA/NVA categories | Only flat labels | ✅ Productive/Delay/Non-productive |
| Multiple subjects | One user at a time | ✅ Multiple stations |
| Confidence intervals | ❌ Not available | ✅ In reports |
✅ Our app is specialised
We are not a generalist "time tracking" app. We implement the specific technical requirements of Work Sampling: randomness, statistical calculation, Lean categorisation, and instantaneous observations.
Complementary Use
In a complete methods engineering project, both techniques complement each other:
- Phase 1 - Diagnosis (Sampling): Identify what percentage of time is lost in delays, waits and non-productive activities.
- Phase 2 - Detail (Time Study): For the productive operations identified, time the specific cycles to establish standard times.
- Phase 3 - Follow-up (Sampling): After implementing improvements, run another sampling to validate that delays were reduced.