A time study is a structured technique used to measure the work content of a task and establish the standard time required for its completion. This methodology provides the foundation for accurate labor costing, production scheduling, and operational efficiency. Understanding the process allows organizations to set production goals and identify areas for improvement. The following steps detail how to conduct a time study effectively to generate reliable work standards.
Preparation and Job Selection
The initial phase of a time study involves careful selection and preparation. A job should be selected based on specific criteria, such as high production volume, its function as a process bottleneck, or its designation as a newly implemented procedure. Focusing the study on these areas yields the greatest return on the investment of time and resources.
Once the job is selected, the operator must be informed about the purpose and scope of the study. This communication minimizes anxiety and reduces the Hawthorne effect, where workers temporarily change their behavior because they know they are being observed. The observer must also be selected and trained thoroughly to ensure consistency in measurement technique and objectivity in data recording.
Decompose the Task into Measurable Elements
Breaking the overall job into smaller, discrete elements is necessary for accurate timing. Each element should be distinct, short, and repetitive, typically lasting between 0.03 and 0.10 minutes to allow for precise measurement. This segmentation helps identify different types of work and non-work activities within the overall cycle.
Elements are categorized into constant elements, which take the same time regardless of process variables, and variable elements, whose time changes based on factors like size, weight, or distance. Defining clear breakpoints for each element is necessary, as these precise points signal the start and end of one element and the beginning of the next. A breakpoint might be defined as the instant the operator’s hand grasps a tool or the moment a part contacts a machine surface, ensuring consistent measurement.
Data Collection and Timing the Cycles
Timing the elements involves collecting raw data using specific methods. The two primary methods are continuous timing and snapback timing, with the continuous method generally preferred for its accuracy. Continuous timing involves letting the stopwatch run without interruption throughout the study, recording the cumulative time at the end of each element’s breakpoint.
Snapback timing involves resetting the stopwatch to zero at the end of each element, which can introduce small errors due to the observer’s reaction time and manual resetting. The observer must determine the appropriate number of cycles to observe, often based on statistical sampling formulas or practical guidelines considering cycle length and desired accuracy. Shorter, repetitive cycles generally require more observations to achieve a reliable average.
During the observation, the observer records the raw times and notes any “foreign elements”—activities that are non-standard, unnecessary, or unrelated to the defined work cycle. After the observation, the recorded times for each element are analyzed to exclude abnormal readings caused by foreign elements or errors. The average observed time for each element is then calculated from the remaining, validated cycle times.
Adjusting Observed Time with Performance Rating
The average observed time must be adjusted to account for the operator’s pace during the study, leading to the calculation of the “Normal Time.” Performance rating is the systematic adjustment applied by the trained observer to quantify the operator’s pace relative to a defined standard. This rating addresses whether the operator was working faster or slower than the average trained worker.
The standard or “normal” pace is defined as 100%, representing the effort level a qualified operator can maintain throughout the workday without undue fatigue. If the observer judges the operator to be working 20% faster than normal, a 120% rating is applied; if 10% slower, a 90% rating is used. Standardized systems, such as the Westinghouse system, offer frameworks to help observers consistently assess factors like skill, effort, conditions, and consistency.
The Normal Time is calculated by multiplying the average observed time for the element by the performance rating factor. This calculation normalizes the observed data, removing the variability introduced by the individual operator’s pace. The resulting Normal Time represents the time a standard, qualified operator should take to perform the element under normal working conditions.
Calculating Necessary Allowances
The Normal Time reflects only the time taken for direct work, requiring further adjustment to determine a sustainable standard. Allowances are additions to the Normal Time that account for factors outside of direct work performance and ensure the standard is realistic for a full shift. These allowances fall into three main categories, often referred to as PFD allowances: Personal Needs (P), Fatigue (F), and Delays (D).
The Personal Needs allowance covers necessary interruptions like using the restroom or getting a drink of water, and is typically a fixed percentage applied across all jobs. Fatigue allowances are variable and based on the physical demands of the job, such as weight handled, posture required, or environmental conditions like heat or noise. Delay allowances account for unavoidable interruptions outside the operator’s control, such as waiting for materials or brief equipment adjustments.
The total allowance is converted into an allowance factor, which is used to inflate the Normal Time. This ensures the final standard time includes a reasonable buffer for recovery from fatigue and personal breaks. The calculation involves adding the percentage of the total allowance to one, creating a multiplier applied to the Normal Time.
Determining the Standard Time and Documentation
The final step is the calculation of the Standard Time, which is the time required for a qualified worker to perform a task at a normal pace, including necessary allowances. This calculation is formalized by the formula: Standard Time = Normal Time $\times$ (1 + Allowance Factor). The resulting figure represents the output standard used for planning, scheduling, and incentive systems.
Thorough documentation of the study is important to ensure the standard is defensible and repeatable. The observer must record details including the date of the study, the name of the observer and operator, the specific equipment and tools used, and descriptions of each element. All raw data sheets, including cycle times and performance rating justifications, must be organized and retained. This documentation provides the basis for future process audits, allows for the maintenance of standards, and serves as a reference regarding the established work rate.
Common Pitfalls and Best Practices
Conducting a time study requires navigating several common pitfalls that can compromise accuracy. Observer bias, where preconceived notions about the operator or process influence the performance rating, is a frequent challenge that must be managed. Operator resistance can also skew results, as an uncooperative operator may deliberately slow down or introduce non-standard elements to inflate the observed time.
A poorly defined process or set of elements will lead to an unreliable standard, particularly if the breakpoints are ambiguous or inconsistent. Studying a process that has not been optimized for efficiency is a wasted effort, as the resulting standard will simply lock in existing waste. The process should be streamlined and standardized before the time study is executed.
To ensure the quality of the standard, best practices should be implemented. It is beneficial to train multiple observers and conduct periodic consistency checks to ensure uniformity in performance rating. Results should be validated by comparing the calculated standard time against historical production data or similar standards. Any process that undergoes significant changes, such as new machinery, method improvements, or material substitutions, should be periodically re-studied to ensure the established standard remains accurate and relevant.