Compare and estimate
In the REFA methodology , comparing and estimating refers to methodical means for determining standard times . If the volume of a work order is not sufficiently large, in the case of rarely occurring processes or only for calculation, etc., there is no economical method of measuring standard times. In order to still be able to work with sufficiently reliable information, the method comparing and estimating was developed.
Basics
In REFA methodology, comparing is defined as
"Comparing is generally understood to mean juxtaposing things or facts in order to determine differences or similarities"
Accordingly, a qualitative difference is determined when comparing. In addition, estimating determines quantitative data and is defined as follows:
“Estimating is the approximate determination of quantifiable data. It is characteristic that estimated data can always be measured. "
Comparing and estimating in work studies determines standard times by comparing one or more known work processes with another, unknown one. The differences and similarities are determined and the resulting time deviations are estimated.
Methodical aids
The methodology helps to compare and estimate with three methodological influences that must be known to the practitioner in order to achieve good results.
- People's concept of time: People value times based on their experiences with similar processes. Frequently repeated processes are often shorter and less often executed, more varied processes longer than actually estimated. The deviation becomes more pronounced when one is very familiar with the work activity.
- Comparison of the work items: It is often easier to compare the work items with one another instead of the processes.
- Structuring the comparison and estimating: If an overall process is not estimated at once, but the process is divided into portions, the overall result improves because the estimation error is distributed over several parts ( error compensation ).
The REFA standard program for comparing and estimating divides the procedure outlined above into 8 steps:
- Description of the work task and the purpose of the times
- Search for comparable work items
- Comparison of working conditions
- Comparison of work items
- Comparison of work processes
- Determine the times to be added or subtracted
- Determine and add surcharges
- Use determined time as target time
In the case of systematic relationships, the procedure can be simplified and made more precise using an influencing factor calculation ( regression analysis ).
If the process is used because, on the one hand, always small order quantities of, on the other hand, always similar products - a common case in medium-sized manufacturing companies - are produced, a very extensive catalog of comparable work items is quickly created. In this case, the time class method is used for better systematisation and faster application of comparing and estimating with the help of time class catalogs or even planned times .
Individual evidence
- ↑ a b c REFA (Hrsg.): Methodology of work studies: Part 2 data determination . Munich: Carl-Hanser-Verlag, 1978 ( ISBN 3-446-12704-6 ). Page 276–292