What is Work Sampling?
Introduction
Work Sampling is an industrial engineering technique developed by L.H.C. Tippett in the 1930s. It lets you determine how working time is distributed without having to continuously time each activity.
💡 Plain Definition
"Observe what workers are doing at random moments to estimate what share of the time they spend on each activity."
Why use Work Sampling?
Unlike traditional time study (stopwatch-based timing), Work Sampling has several advantages:
✅ Advantages
- • Less intrusive: workers behave more naturally
- • Multiple observers: several workers can be observed at once
- • More economical: less analyst time required
- • Unbiased: random instants give representative data
- • Statistically valid: results carry a confidence interval
📊 Use Cases
- • Measure productivity: % of productive time
- • Identify delays: root causes of lost time
- • Justify headcount: data to hire or reassign staff
- • Improve processes: detect bottlenecks
- • Calculate costs: cost of each task
Practical Example
Imagine you observe a machine operator 100 times over a week, at completely random moments. The results could be:
| Activity | Category | Observations | % |
|---|---|---|---|
| Operating machine | Productive | 45 | 45% |
| Loading material | Productive | 20 | 20% |
| Waiting for material | Delay | 18 | 18% |
| Maintenance | Productive | 10 | 10% |
| Conversing | Non-productive | 7 | 7% |
| TOTAL | 100 | 100% | |
Interpretation: the operator is productive 75% of the time (45% + 20% + 10%). They lose 18% waiting for material (logistics improvement opportunity) and 7% in non-productive time.
Statistical Foundation
The validity of sampling rests on probability theory. The more observations you take, the more precise the result.
Sample size formula
n = Z² × p × (1 − p) / E²
Where: Z = confidence level, p = proportion, E = max error
Don't worry, the app calculates all of this for you automatically. You only need to set the desired confidence level and precision.
What you will learn in this course
Across the next lessons you will learn to:
- Install and configure the app
- Create studies with the right parameters
- Define jobs and tasks to observe
- Generate random observation plans
- Register observations quickly
- Analyse results with interactive charts
- Export professional reports to Excel
🎯 Goal of This Lesson
You now understand what Work Sampling is and what it is for. In the next lesson you will install the app as a PWA on your device.