Time Study Techniques

Why This Matters

Time study techniques form the backbone of industrial engineering's core mission: making work more efficient. You're being tested on your ability to understand not just what these techniques are, but when to apply each one and how they connect to establishing fair, accurate standard times. Every technique in this guide ultimately feeds into the same goal—determining how long a task should take under normal conditions, which then drives decisions about staffing, scheduling, costing, and process improvement.

The key concepts you'll encounter repeatedly include direct vs. indirect measurement, statistical sampling vs. continuous observation, and the relationship between observed time, normal time, and standard time. Don't just memorize definitions—know which technique solves which problem, and understand the mathematical relationships that tie raw observations to usable standards. When an exam question asks you to recommend a measurement approach or calculate a standard time, you need to recognize the underlying principles at work.

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Direct Observation Methods

These techniques involve watching work as it happens and recording times in real-time. Direct observation provides high accuracy for specific tasks but requires significant analyst time and can influence worker behavior.

Stopwatch Time Study

• Most fundamental direct measurement technique—uses a stopwatch to capture actual elapsed time for defined work elements
• Requires element breakdown to separate tasks into measurable components, typically targeting elements between 3-10 seconds
• Foundation for standard time calculations when combined with performance rating and allowances

Continuous Timing Method

• Records cumulative elapsed time throughout the entire work cycle without stopping the watch
• Reduces timing errors since the analyst never resets the stopwatch mid-study, eliminating missed time between elements
• Best for smooth, flowing operations where elements transition naturally without clear stopping points

Snapback Timing Method

• Resets stopwatch to zero after each element, providing individual element times directly
• Ideal for tasks with distinct phases or when elements vary significantly in duration
• Higher risk of timing loss during reset—small gaps accumulate, potentially underestimating total cycle time

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Indirect Measurement Methods

These approaches estimate task times without observing every instance. Indirect methods trade some precision for efficiency, making them ideal for non-repetitive work or preliminary analysis.

Work Sampling

• Statistical technique using random observations to estimate the proportion of time spent on different activities
• Sample size determines accuracy—calculated using $n = \frac{z^2 \cdot p(1-p)}{e^2}$ where $p$ is the estimated proportion and $e$ is desired error margin
• Cost-effective for analyzing multiple workers or machines simultaneously across extended periods

Predetermined Motion Time Systems (PMTS)

• Assigns standard times to basic human motions like reach, grasp, move, and release—no direct observation required
• MTM (Methods-Time Measurement) is the most widely used system, expressing times in TMUs (1 TMU = 0.00001 hours)
• Enables time estimation before a job exists, making it essential for workstation design and method comparison

Standard Data Systems

• Compiles historical time data from previous studies into reusable databases organized by task characteristics
• Regression equations or lookup tables allow rapid estimation for similar new tasks
• Bridges the gap between PMTS precision and stopwatch study effort—faster than direct observation, more job-specific than generic motion times

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Technology-Enhanced Methods

Modern tools increase measurement accuracy, reduce analyst effort, and enable analysis that manual methods cannot achieve.

Video Analysis

• Permanent visual record allows repeated review, frame-by-frame analysis, and measurement verification
• Eliminates observer effect since workers often forget about cameras over time, capturing more natural performance
• Supports training and method improvement by providing concrete evidence of current practices and proposed changes

Computerized Work Measurement

• Software automates data capture through barcode scanning, sensor integration, or digital input devices
• Real-time dashboards enable immediate performance feedback and trend identification
• Integrates with enterprise systems for automatic updating of labor standards, routing files, and cost estimates

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Analysis and Breakdown Techniques

Before measuring time, analysts must structure the work into measurable components. Proper task decomposition is essential—poorly defined elements lead to inconsistent measurements and unusable standards.

Element Breakdown

• Divides operations into discrete, measurable work units with clear start and end points (called breakpoints)
• Elements should be as short as accurately measurable (typically 0.03-0.05 minutes minimum) but represent complete motions
• Separates machine time from manual time and constant elements from variable elements for accurate analysis

Cycle Time Analysis

• Measures total time for one complete unit of output, from start of first element to start of next cycle
• Identifies bottlenecks by comparing individual element times and highlighting where delays accumulate
• Critical for line balancing—cycle time determines maximum production rate: $\text{Output Rate} = \frac{\text{Available Time}}{\text{Cycle Time}}$

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Time Adjustment and Standardization

Raw observed times must be adjusted to reflect what a qualified worker should achieve under normal conditions. This is where time study becomes both science and judgment.

Performance Rating

• Compares observed worker pace to a conceptual "normal" performance level, expressed as a percentage (100% = normal)
• Leveling systems like Westinghouse evaluate skill, effort, conditions, and consistency separately
• Most subjective step in time study—requires trained analysts and consistent rating scales to ensure fair standards

Normal Time Calculation

• Adjusts observed time for worker performance: $\text{Normal Time} = \text{Observed Time} \times \frac{\text{Performance Rating}}{100}$
• Represents time for a qualified worker performing at sustainable pace without allowances
• Averages multiple observations to account for natural variation in task completion

Allowances Calculation

• Adds time for unavoidable delays including personal needs (typically 5%), fatigue (varies by physical demands), and unavoidable delays
• Expressed as percentage of normal time or as fixed time additions depending on company policy
• PFD allowances (Personal, Fatigue, Delay) ensure standards reflect realistic, sustainable performance expectations

Standard Time Calculation

• Final output of time study process: $\text{Standard Time} = \text{Normal Time} \times (1 + \text{Allowance Factor})$
• Serves as benchmark for scheduling, costing, incentive systems, and performance evaluation
• Must be documented and maintained—standards require periodic review as methods, equipment, or conditions change

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Documentation and Quality Control

Systematic recording ensures studies are reproducible, defensible, and useful for future reference.

Time Study Forms and Documentation

• Standardized forms capture element descriptions, observed times, ratings, and allowance calculations in consistent format
• Supports audit trails for labor negotiations, method changes, and standard revisions
• Digital documentation systems enable searchability, version control, and integration with standard data databases

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Quick Reference Table

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Self-Check Questions

1. A task has an observed time of 2.4 minutes and a performance rating of 110%. If total allowances are 15%, what is the standard time? Walk through each calculation step.

2. Which two techniques would you recommend for establishing times on a new product before production begins, and why can't you use stopwatch time study?

3. Compare work sampling and stopwatch time study: under what conditions would each be the better choice?

4. An analyst using the snapback method consistently gets lower total cycle times than one using continuous timing on the same operation. Explain the most likely cause.

5. Why must performance rating occur before allowances are added? What would happen to the standard time calculation if you reversed this sequence?