Work Measurement Techniques

Why This Matters

Work measurement is the backbone of industrial engineering—it's how we answer the fundamental question: how long should this task actually take? Without accurate time standards, you can't set fair wages, balance production lines, estimate costs, or identify inefficiencies. Every concept you'll encounter in operations management, from capacity planning to labor cost estimation, depends on the techniques covered here.

You're being tested on more than just knowing that a stopwatch measures time. Exams will ask you to select the right technique for a given situation, compare the trade-offs between direct observation and predetermined systems, and explain when statistical sampling beats continuous measurement. Don't just memorize definitions—know what problem each technique solves and when you'd choose one over another.

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Direct Observation Methods

These techniques require someone to physically watch and record work as it happens. They capture actual performance in real conditions, which makes them highly accurate but also time-consuming and potentially subject to observer effects.

Time Study

• Continuous observation of task cycles—the analyst watches workers complete full task cycles while recording elapsed times for each element
• Rating factor adjustment accounts for whether the observed worker is performing faster or slower than a normal pace, ensuring standards reflect average performance
• Multiple observations required to capture natural variability; typically 10-30 cycles depending on cycle length and desired confidence level

Stopwatch Method

• Direct timing with manual recording—the most fundamental measurement approach, using either continuous timing or snapback (reset after each element)
• Element breakdown divides tasks into discrete, measurable components with clear start and end points for consistent measurement
• Observer bias risk means results can vary between analysts; standardized procedures and multiple trials help ensure repeatability

Video Analysis

• Permanent visual record allows multiple analysts to review the same work cycle, eliminating the need for real-time decisions about element boundaries
• Frame-by-frame precision enables measurement accuracy down to $\frac{1}{30}$ second (at 30 fps), far exceeding manual stopwatch capability
• Training and feedback applications extend beyond measurement—recordings become powerful tools for methods improvement and worker development

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Statistical Sampling Approaches

When continuous observation isn't practical—think long cycle times, multiple workers, or varied activities—statistical methods let you draw valid conclusions from samples rather than complete data.

Work Sampling

• Random observations at intervals estimate the percentage of time spent on different activities without watching continuously
• Statistical confidence depends on sample size; the formula $n = \frac{z^2 \cdot p(1-p)}{e^2}$ determines how many observations you need for desired precision
• Ideal for indirect work like maintenance, supervision, or office tasks where cycle times are irregular or undefined

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Predetermined Motion Time Systems (PMTS)

These systems bypass direct observation entirely by assigning pre-established time values to basic human motions. If you can describe what motions a task requires, you can calculate its standard time before anyone performs it.

Predetermined Motion Time Systems (PMTS)

• Basic motion building blocks—all manual work is decomposed into fundamental movements like reach, grasp, move, and release
• Time values from research are derived from extensive industrial studies and expressed in TMUs (time measurement units, where 1 TMU = 0.00001 hours or 0.036 seconds)
• Methods design capability lets engineers evaluate alternative work methods before implementation, comparing theoretical times to select the most efficient approach

Methods-Time Measurement (MTM)

• Most widely used PMTS with detailed tables covering motions like $\text{Reach}$, $\text{Grasp}$, $\text{Move}$, $\text{Position}$, and $\text{Release}$
• MTM-1, MTM-2, MTM-3 variants offer different levels of detail; MTM-1 is most precise but time-consuming, while MTM-3 uses broader motion categories for faster analysis
• Eliminates performance rating since times come from standardized tables, removing a major source of subjectivity in traditional time study

Maynard Operation Sequence Technique (MOST)

• Sequence-based analysis groups motions into logical patterns: General Move, Controlled Move, and Tool Use sequences
• Faster application than MTM—typically 5-10 times quicker to apply while maintaining accuracy within $\pm 5\%$ of MTM results
• Index values replace detailed motion analysis; analysts select parameters describing distance, weight, and placement difficulty

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Data-Based Systems

These approaches leverage accumulated measurement data to speed up future analyses. Instead of measuring from scratch, you reference established standards for similar work.

Standard Data Systems

• Historical time databases compile element times from previous studies, organized by operation type, machine, or product family
• Rapid estimation for new jobs by combining pre-measured elements; if you've timed "drill 1/4" hole" before, you don't need to time it again
• Consistency across projects ensures similar tasks receive similar time standards, reducing disputes and improving cost estimation accuracy

Synthetic Time Systems

• Hybrid methodology combines elements from direct observation, PMTS, and standard data to handle unique or complex operations
• Interpolation and adjustment allows engineers to estimate times for tasks that don't exactly match existing standards
• Flexibility for non-standard work makes this approach valuable in job shops or custom manufacturing where pure PMTS may not fit

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Technology-Enhanced Methods

Modern systems automate data collection and analysis, reducing human effort and enabling capabilities impossible with manual methods.

Computerized Work Measurement Systems

• Automated data capture using sensors, barcode scanners, or machine interfaces eliminates manual recording errors
• Real-time analysis provides immediate feedback on cycle times, enabling quick identification of bottlenecks and abnormal conditions
• Integration with MES/ERP connects measurement data to broader manufacturing execution and enterprise resource planning systems for comprehensive productivity tracking

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Quick Reference Table

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Self-Check Questions

1. A plant manager needs to determine what percentage of time maintenance workers spend on preventive vs. reactive tasks. Which technique is most appropriate, and why wouldn't traditional time study work well here?

2. Compare MTM and MOST: what do they have in common, and when would you choose MOST over MTM for a work measurement project?

3. An engineer is designing a new assembly workstation and needs to estimate cycle time before building it. Which category of techniques allows this, and what's the main advantage over direct observation methods?

4. What's the key difference between standard data systems and PMTS in terms of where the time values originate? When might you use both together?

5. If an FRQ asks you to recommend a measurement technique for a high-volume, short-cycle assembly operation where workers might change their pace when observed, which two techniques would you compare, and what trade-offs would you discuss?