ORDREL / LEARN · ENGLISH
Time Study: Observations, Standard Time and Allowances
A time study first records comparable observations under a defined method. An observed average is not automatically a standard time. Any performance rating and allowance must have an explicit, justified basis; ORDREL records observations but does not certify a labor standard.
Define what one observation means
Name the process, product, start event and end event. Decide whether you are timing successive completions, variable batches, identical parallel resources or individual task elements. Keep those modes distinct. Record conditions such as product mix and interruption rules without putting personal or confidential operational data in a public example.
Observe the actual agreed method with the team. Include normal variation; do not quietly remove slow observations. If a measurement is interrupted or outside scope, retain it with an exclusion reason. Small practice samples illustrate arithmetic but do not establish the sample size needed for a dependable production standard.
An observed-time example, not a validated standard
Fictional manufacturing teaching example. These figures are not ORDREL customer results.
Five comparable single-unit completion observations are 54, 60, 66, 60 and 60 seconds. Their sum is 300 seconds across five units, so mean observed time = 300 ÷ 5 = 60 seconds per unit. Median is also 60 seconds. The equal median does not prove low variation or representative sampling.
For a separate demonstration of standard-time conventions, suppose a qualified study process justifies a 110% performance rating. Normal time = 60 × 1.10 = 66 seconds. A higher rating here means the observed work was faster than the reference pace, so the adjusted normal time is longer. The 110% is a fictional assumption, not an ORDREL recommendation.
| Convention | Calculation | Result |
|---|---|---|
| Allowance is 15% of normal time | 66 × (1 + 0.15) | 75.9 seconds |
| Allowance is 15% of standard time | 66 ÷ (1 − 0.15) | 77.6471 seconds |
These formulas answer different questions. Do not label both “15% allowance” without stating the denominator. Neither percentage should be adopted from this example; use your organization’s competent work-measurement and working-condition review.
What ORDREL actually calculates
In Time Study Lab, choose completion-interval mode, one unit and one resource, then record the five observations. With 480 scheduled minutes, 60 break minutes and demand 420, available time is 25,200 seconds and takt is 60 seconds/unit. The observed mean equals takt and the modeled capacity is 420 units.
The tool reports observed statistics, classifications and compatible capacity comparisons. It does not apply the rating and allowance calculations above or approve a standard time. Perform that separately with a documented method. For individual task mode, do not turn a mixed list of elements into a pooled production rate.
Review representativeness and uncertainty
Compare samples across the conditions that matter: startup versus steady operation, different product families, method versions and trained operators. Keep the measurement purpose clear. A completion interval at the output of a line includes the effect of the whole line; a manual element time does not.
For variable batches, divide total observed seconds by total units rather than averaging unlike batch ratios. For instance, 100 seconds for 10 units and 300 seconds for 20 units give 400 ÷ 30 = 13.3333 seconds/unit, not the simple average of 10 and 15 seconds/unit.
Common mistakes
- A short sample is a teaching example, not proof of a stable standard.
- A machine’s ideal cycle for OEE is not automatically the observed average.
- Adding allowances to a rate already containing the same delays double counts them.
- Changing the work method invalidates an unqualified comparison with the old standard.
- Do not use a timing exercise as a substitute for ergonomics, safe-work requirements or fair consultation.
Sources and method notes
Sources support the method definitions. Examples, interpretation and tool instructions are ORDREL teaching material, not an endorsement by the referenced organizations. See methods and corrections.