Statistical Parameters
Why Are They Important?
Statistical parameters determine how many observations you need for your study to be scientifically valid. It's not an arbitrary number, but a mathematically calculated one.
1. Confidence Level
It is the probability that your results are correct. The app offers three options:
What does 95% mean? That if you repeated the study 100 times, 95 of those times you would obtain results within the error margin you configure.
2. Error Margin (Precision)
It is the maximum acceptable error in your results. It's expressed as ±X%.
If your result is 68% productive with an error margin of ±5%
The real value is between 63% and 73%
| Error Margin | Typical Use | Observations (approx.) |
|---|---|---|
| ±10% | Quick exploratory studies | ~100 |
| ±5% ⭐ | Standard studies (recommended) | ~385 |
| ±3% | Important decisions | ~1,067 |
| ±1% | High precision (expensive) | ~9,604 |
3. Estimated Proportion (p)
It is your initial estimate of the percentage of time the worker spends on the main activity (productive).
💡 Which value to use?
- • If you have no idea: use 50% (maximum sample)
- • If you have previous data: use that percentage
- • If you ran a pilot study: use the preliminary result
4. Allowances
Additional percentage added to normal time to calculate the standard time. It includes:
- Personal needs: ~5% (restroom, water)
- Basic fatigue: ~4%
- Variable fatigue: Depends on conditions
Typical value: 15% for standard industrial work.
Automatic Calculation
The application automatically calculates how many observations you need:
With the selected parameters:
385
observations required
Pacing Rating Scale
If you're going to rate the work pace, choose the scale you use:
- 100-133 (ILO/Centesimal): 100 = normal, 133 = maximum incentive
- 60-80 (Bedaux/BSI): 60 = normal, 80 = maximum incentive
Recommended Configuration
For a standard study, we recommend:
⭐ Recommended Configuration
- Confidence Level
- 95%
- Error Margin
- ±5%
- Estimated Proportion
- 50%
- Allowances
- 15%
Result: ~385 observations for a valid study
🎯 Next Step
The parameters are configured. Now we need to define what we'll observe: the work stations.