Work Measurement and Time Standards
Work measurement establishes the time a qualified, trained worker needs to perform a task at a defined performance level with specified methods. Candidates must distinguish time-study methods: stopwatch time study, predetermined time systems (MTM, MOST), standard data, work sampling, and historical data. Know the stopwatch procedure: select and train the worker, divide the job into elements (with breakpoints that are easy to time), record ratings, take enough cycles, apply allowances, and compute the standard.
The core arithmetic is tested repeatedly. Observed time is rated to normal time: Normal time = Observed time × Performance rating. Standard time adds allowances: Standard time = Normal time × (1 + allowance fraction) or Normal time / (1 − allowance fraction) depending on whether allowances are expressed as a percentage of normal time or of total time. Traps: using the wrong allowance base; forgetting that rating >100% for a fast worker increases normal time; and confusing standard time with normal time. Also know the required number of cycles formula using the t-distribution: n = (z·s / (k·x̄))², where k is the desired precision.
Work sampling estimates the proportion of time in an activity; sample size n = z²p(1−p)/e². Predetermined systems require no performance rating because the elemental times are already at a defined pace. Allowances include personal, fatigue, and delay (PFD); foreign-element and machine-controlled times are handled separately.
Worked example
Observed time = 4.0 min, rating = 110%, allowance = 15% of normal time. Normal = 4.0 × 1.10 = 4.40 min. Standard = 4.40 × 1.15 = 5.06 min. If a question states allowances as 15% of total time, use 4.40 / (1 − 0.15) = 5.18 min instead.