After reading this short article you will learn about:- 1. An interpretation of occupational Sampling 2. Definition of work Sampling 3. Concept 4. Procedure 5. Applications 6. Benefits 7. Limitations.

Meaning of occupational Sampling:

Work sampling is a statistically based technique utilized because that analysing work-related performance and device utilization by direct observation, yet without a avoid watch. So job-related sampling is another useful an approach of occupational study.

This method is particularly useful to calculation the proportion of delays or idleness’s developing in a enterprise/plant and attributing the cause for it, together as power failures/input delays, maker cleaning, device breakdowns and manpower idling or in other words, estimating ratio of time invested by an executive in attending meetings, telephoning or analysis etc.

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The protect against watch technique for time estimation is very time consuming and also therefore not feasible.

Work sampling is a an approach for creating standard times of activities. This an approach also recognized as task sampling was devised by L.H.C. Tippet in 1934. This method is much more suitable for analysing group activities and repetitive tasks which take longer duration.

If a provided individual performs more than one activity, then the time standard for each activity can be computed with the help of this method. For example, on a printing press, a solitary operator/worker will certainly be doing composing, proofreading, to press etc. The time criter for all these tasks can be established with the help of occupational sampling method.

The technique of work sampling is composed of acquisition a large number the instantaneous monitorings randomly, quite than taking observations continuously as is done in miscellaneous production investigations/ studies. This technique is a sampling an approach and relies upon regulations of probability.


A sample taken at arbitrarily from a big population provides a an excellent estimate of the circulation of the population because it often tends to have actually the same distribution as the population.

Some examples are together follows:

(1) A decision regarding the cooking of rice is take away by having a sample of rice native a boiling/ cooking pot and also pressed in between fingers.

(2) A decision concerning the top quality of wheat bag to it is in purchased is do by evaluating a sample that wheat indigenous a bag.


Hence, work-related sampling is a technique of identify the percentage cases of a certain activity (a group of processes, machines, or workers) with the help of statistical sampling and random observations. Once the sample dimension is big enough and random observations are do indeed, there is fairly a high probability the the monitorings would reflect the real instance plus minus a details margin that error.

Definition of job-related Sampling:

“Work sampling is a method in which a big number of instantaneous observations are do at random time intervals end a duration of time or a team of machines, employees or processes/operations. Each monitoring records what is continue at that instant and the percentage of monitorings recorded because that a details activity or delay/idleness is a measure up of the percent of time throughout which that task or delay/idleness occurs”.

Work sampling has a long and also impressive perform of applications but every one of them fall, into one the the complying with three categories:

(i) job-related sampling can be offered as proportion study that working and idle times.


(ii) It can be used as power sampling research in i m sorry working and idleness on functioning times are measured and, a performance index is prepared.

(iii) If can be used as a job-related measurement technique.

Theory of occupational Sampling:

It states that the percentage of observations recorded on one operation/process in any type of state is a trusted estimate that the percentage time the operation/process is in the state, provided, “sufficient number of observations is taken at random”.

It may be provided that here, specific stress should be payment on the indigenous “random” and also “sufficient variety of observations”. In this technique, part error might occur but the size of error has tendency to decrease together the variety of samples increases.


Work sampling is a sampling technique and relies upon the regulations of probability. A sample bring away at arbitrarily from a big population offers a good estimate the the distribution of the population. To do it more clear, permit us consider the following example.

A worker when working throughout his shift either walk the project assigned come him or stay idle for one or the other reason. The adhering to table shows that the end of complete 50 observations, there were 45 working observations and also five idle observations.


This table suggests the functioning time and also idle time.


In this example, the idle time percent would it is in -5/50x 100 =10%

Working time would certainly be x 100 = 90%

This examination is because that one worker for a change of 8 hrs a day and also indicates that the operator to be idle for 10% or 48 minute in a shift of 8 hrs (480 minutes) while working for 90% or 432 minutes in one shift.

Confidence Levels:

The an outcome obtained by work-related sampling an approach differs considerably from the results actually achieved by constant recording the time. The accuracy of an outcome depends ~ above the number or observations and also the limits of confidence level since the sampling procedure used involves particular degree the error. So the is necessary to decide, what level of to trust is preferred in the last “Work Sampling” results.


During a investigation, if we boost the variety of observations considerably and in each observation then variety of activities are large we can attain a smoother curve dubbed normal circulation curve as displayed in Fig. 18.12.


The most common confidence level is 95%. The area under the curve at 2 sigma or two traditional deviations is 95.45% which is rounded off provides 95%.

This suggests that the probability is 95% of the time the random, observations will be true or represents the fact and 5% of the time false or will certainly not. For bulk of cases, one accuracy that 5% is taken into consideration satisfactory. This is usually described as the percentage standard error.

Sample dimension Determination. To obtain a wanted accuracy level an analyst is forced to take sufficient variety of observations.

Following formula might be used for recognize the requisite number of observation in stimulate to accomplish the desired accuracy:


Limit that error = Sp = x √p(1-p)/N

Where x = 1. 2 or 3 because that confidence level the 68%, 95% and 99% or one sigma, two sigma 3 sigma confidence level respectively.

S = preferred relative accuracy.

P = Percentage incident of an activity or delay expressed in decimal e.g., 10% = 0.10

N = Sample dimension or total number of random observations.

Example 1:


Assume a to trust level the 95% and desired relative accuracy that ±5%. Identify the variety of observation compelled for the study. The job-related sampling technique is to be offered to identify the use of a group of drilling machines. The Preliminary study shows that the machines are utilized for about 60% that the time.


Example 2:

A work-related sampling investigation was conducted to estimate the moment for which the workers in plant continue to be idle.

A complete of 720 monitorings were made around the workers. In 45 monitorings the employees were found idle. If the to trust level is 95% recognize the absolute accuracy the the present estimate that the relationship of time spend by idleness.




Total no. Of observations N =120

P = proportion of idle time = 45/720 = 0.0625


Work Sampling Procedure:

The procedure to be adopted for conducting a job-related sampling examination will count upon the form of application. As lot as possible different techniques will be used for taking observations. An analysis of the data candlestick be performed to fit the case.

But the complying with general procedure is applicable in every study:


(1) Define the Problem:

State the key objectives or objective of the study clearly. This invariably includes the detailed summary of each facet of the work. The analyst must explicitly know what room the various states that the operator’s activity which space to be observed. Occasionally it will be required to observe the operator together either functioning or idle.

(2) style a chart for recording information’s.

(3) do a pilot examine i.e………… preliminary observation.

(4) indigenous the preliminary observations, compute the hold-up percentage p.

(5) determine the accuracy and confidence level desired for the investigation.

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(6) attain the approval of the foreman of the room or section head pertained to in which examine is to it is in made. Obtain the teamwork of the workers/operators to be studied and also they should likewise understand the aim/purpose that study.

(7) calculation the variety of observations forced for a preferred level of confidence and also accuracy. Because work sampling is a statistics sampling procedure and also the estimate obtained would become more and much more realistic together the sample dimension increases.

Thus, an ext number of monitorings will make the study more accurate. Through this increase in number of observations, the cost and time of examine would increase. For this reason the variety of observations to it is in taken are determined in the irradiate of precision and confidence required.

(8) identify the number of observers needed. Select and also instruct these people.

(9) recognize the variety of days/shifts forced for the study.

(10) plan the schedule of monitorings such together time for taking and the route to be complied with by the observer.

(11)Proceed through sampling of monitorings in the chart (record sheet) making note of any kind of unusual points.

(12) Analysing the data and presenting the results. The work-related sampling data are analysed during the research in order to inspect if the things space going according to plan or not. The data is typically summarized in ~ the finish of every day.

This gives the tendency for the following day’s work and also gives information regarding precision acquired in the research so far and also how much much more is required. At the end of study, the final evaluation are performed and also required results are presented. This would carry out either ratio delay, power study-or-work measurement.

Applications/Uses of job-related Sampling:

Work sampling is a very useful technique to solve selection of problems in various varieties of tasks involving teams of machines, procedures or people. With the expansion and also growth of industrial plants/ enterprises it has become increasingly difficult for executives/managers to collection information and facts about what goes on in their manufacturing sections.

Work sampling is useful and also can be applied when:

(1) occupational of teams needs to be investigated/studied.

(2) there is clear difference between functioning time and also idle time.

(3) to indicate areas of delay.

(4) come investigate and to locate areas underutilization.

(5) for establishing as whole performance levels.

(6) For decision of an equipment utilizations.

(7) In determining the distribution of duties amongst a team of workers.

(8) In the study of nature, causes and also extent of interference with effective achievement of a project.

(9) for the objective of price control and also accounting.

(10) To estimate allowances for unpreventable delay.

(11) In ware housing and also shipping operations come pin-point delays therefore that changes in the layout or technique could be figured out which to reduce delays.

(12) it is desired when the expense of making use of other work-related measurement approaches for time a job shows up to be more.

Advantages of work Sampling:

(1) that is a cheaper method than time study and production study.

(2) only one analyst deserve to perform work sampling examine of plenty of activities.

(3) Observers does no require lot training.

(4) the is an ext useful in non-repetitive and also indirect jobs.

(5) plenty of operations or activities which are impractical or i have lot of money to measure up by time study have the right to readily be measured by work-related sampling.

(6) Observations might be made over a period of job or weeks thus decreasing the readjust of day to day or week come week variations.

(7) monitorings are made at random intervals depicting the usual program of the worker together against continuous observations of a worker for a lengthy time over time study which might not disclose his usual program (being mindful of being observed).

(8) The job-related sampling may be interrupted at any time without affecting this results.

(9) The study can be made with pre assigned level of reliability.

(10) The research is much less tiring and less tedious.

(11) that is less time consuming.

(12) as the research is spread out over a number days, that is likely to be an ext representative and also is less impacted by day to day variations.

Limitations of occupational Sampling:

(1) contrasted to time study, the statistical method of work-related sampling examine is challenging to be taken by worker.

(2) The operators might not understand value the sample size and also accuracy etc.

(3) the is no economical for the examine of jobs of short duration or operators and also machines, spread out or located over vast area.

(4) The worker may adjust his occupational patterns ~ above the vision of work-related sampling observer and try to look more productive, result incorrect info which are meaningless.