Work Sampling Study
Work sampling is a technique used to estimate the percentage of time spent on various activities without continuous observation.
Sample Size (n) = (Z² × p × (1 - p)) / E²
Where:
- Z = Z-value for desired confidence level (1.96 for 95%)
- p = Estimated proportion of time spent on activity
- E = Desired margin of error (e.g., 0.05 for ±5%)
Study Parameters
Activities
Enter the activities you want to measure and their observed frequencies:
| Activity | Observed Count | Total Observations | Percentage | Action |
|---|---|---|---|---|
| 75.0% | ||||
| 25.0% |
Work Sampling Results
Total Observations
Samples Collected
Required Samples
For Desired Accuracy
Confidence Level
Study Reliability
Margin of Error
± Percentage Points
Activity Breakdown
| Activity | Count | Percentage | Confidence Interval | Required Samples |
|---|
Interpretation Guidelines
| Sample Size | Reliability |
|---|---|
| < 100 | Preliminary estimate only |
| 100 - 500 | Fair reliability for most applications |
| 500 - 1000 | Good reliability for important decisions |
| > 1000 | High reliability for critical applications |
Practical Examples
Example 1: Machine Utilization
Confidence: 95%, Error: ±5%, Working: 75/100, Idle: 25/100
Results: Working 75% (±8.5%), Required samples: 289
Example 2: Office Work
Confidence: 95%, Error: ±3%, Email: 30/100, Meetings: 20/100, Focus Work: 50/100
Results: Focus Work 50% (±4.9%), Required samples: 1067
Example 3: Hospital Nurse
Confidence: 99%, Error: ±2%, Patient Care: 65/100, Documentation: 25/100, Other: 10/100
Results: Patient Care 65% (±3.8%), Required samples: 5417
Work Sampling Methodology
| Step | Description |
|---|---|
| 1. Define Activities | Identify all possible activities to be measured |
| 2. Preliminary Study | Conduct 50-100 observations to estimate proportions |
| 3. Calculate Sample Size | Determine required observations for desired accuracy |
| 4. Schedule Observations | Randomly distribute observations over time |
| 5. Conduct Study | Record activities at observation points |
| 6. Analyze Results | Calculate percentages and confidence intervals |