Jan #5 - Work and Time Study Flashcards
What is meant by “work measurement”? Why do we use it?
Work measurement is a process by which the time taken to do a unit of work can be determined, and it allows management to optimise productivity by comparing alternate methods and doing initial staffing.
Work measurement is conducted by employing which three principle techniques?
Time study
Work Sampling
Predetermined motion and time systems (PMTS)
A Time Study is one of the three principle techniques used to conduct work measurement. What is a time study?
A time study is a technique whereby the time required by a qualified professional working at a normal pace to do a specific task under specified conditions is measured
A Time Study is a sampling process, so the sample size will affect the associated level of error. What are three important considerations when conduction a time study?
- Level of accuracy
- Level of confidence
- Number of observations
When we are conducting a time study, one important consideration is determining the number of observations we require to achieve a given level of accuracy. How do we calculate this?
Lets say we are conducting a time study where we want to set the standard time to solder the high value resistor to the detector amplifier PCB. We take 10 observations of the 7 elements of the task, then calculate the mean time and standard deviation for each element, as shown below. How do we complete the table if our final figures are to be within 5% of the true long term mean 95% of the time?
Use method shown in picture below to calculate the required number of observations for each element (where the calculation has been done for the ‘unpack resistor’ element). Then, using this number of observations, find the revised mean for each element.
Work Sampling is one of the three principle techniques used to conduct work measurement. What is it, and where is it useful?
Work sampling is used to estimate the proportion of time spent by a worker/machine on various activities and the corresponding idle time. It is useful for jobs with non-repetitive elements.
Work sampling helps in determining how employees allocate their time by making random observations of the activity the worker is performing. List 4 associated benefits
Helps with…
- Setting staffing levels
- Reassigning duties
- Estimating various costs
- Setting delay allowances.
In Work Sampling, we get more accuracy with increasing observations, but there is a limit above which it would not make economic sense to take more observations. What is the equation used to determine the appropriate number of observations in Work Sampling?
Lets say we are conducting Work Sampling for some task where it has been estimated that employees are idle 20% of the time. If the manager wants a work sample with an accuracy of 4% and a desired confidence level of 95.45%, how many observations should they make? Use table below.
List 7 advantages associated with Work Sampling
- Less expensive
- Minimal training needed
- Able to observe many workers/machines simultaneously
- Less anxiety/tension among workers
- Minimal interferance with work
- Directly measures utilisation
- Can be interrupted with no impact on results.
List 5 disadvantages associated with Work Sampling
- Not economical for single operator or several operators over wide area
- Doesn’t provide detailed information
- Offers little value in improving work methods
- Lots of groundwork is required
- No information about individual differences
List 4 situations in which Work Sampling is the most appropriate work measurement technique
- Group activities
- Non-repetitive activities with long cycle times
- Activities that aren’t rigidly constrained by time
- Heterogeneous activities
Predetermined motion and time systems (PMTS) is one of the three work measurement techniques that can be conducted. How does PMTS work?
A task is subdivided into elemental motions, and then pre-set standard times are assigned to those motions. We can then sum these to obtain a standard time for the whole task. Each job element is independent and additive.
What do learning curves show, and for what type of work? How do we define learning in this sense?
Learning curves show that for repetitive work, productivity increases due to the worker gaining skill over time. Learning is defined as the percentage reduction in the time required to make a unit.
Learning curve theory predicts that a doubling of the total number of units causes a constant decrease in time per unit. Studies have shown that the time per unit of the ‘2x-th’ unit is 80% of the time per unit of the ‘x-th’ unit, as shown below. What is the equation used to find the time to complete the n-th unit?
