Tài liệu Wts_5_work_sampling

Work Sampling Work and Time Studies Vietnamese German University Dr.-Ing. Marlene Helfert 2016 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 1 Work sampling Contents Work sampling Description Application example History Characteristics Implementation of work sampling REFA standard program work sampling Goal determination Definition of activities to record Preparation of notations  Scope of observations Tour planning / employee training Technical / organizational preparation Test rounds and notations Continuation of notations and intermediate evaluation Final evaluation Summary Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 2 Work sampling Description Work sampling is a method of finding the proportions of total time devoted to various activities that constitute a job or work situation by random sampling. The percentage of time that a process is in a certain activity is obtained by the ratio of observations of the given activity to the total number of observations. Consider an analyst who takes 100 observations of the shop floor at random intervals over several weeks. It was observed that a certain machine was idle in 30 instances for miscellaneous reasons. The estimated idle time of this machine would then be 30% of the working time. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 3 Work sampling Haller-Wedel 1969 in Schlick 2005 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 4 Work sampling Application example Example of work sampling in a large company of the retail industry for need related short-term manpower planning Schlick 2005 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 5 Work sampling Main utilization H1 Cutting Anciliary utilization N1 Bring paper on machine N2 Handle paper in machine N3 Remove product N4 Back gauge running N5 Set up machine, programming Interruption due to the cycle A1 Change or adjust blade A2 Lubricate mach.; clean w.p. A3 Meeting with supervisor A4 Drive palettes Additional utilization Z1 Additional cut Interruption due to dysfunction S1 Minor maintenance works S2 Further enquiry at other areas S3 Programm correction Interruption due to recovery E1 Recovery at workplace Interruption personal reasons P1 Drink break P2 Other personal breaks L1 Not in use X1 Not identifiable REFA 1997 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 6 Work sampling History L. H. C. Tippett first applied work sampling in the British textile industry during the early 1930s. The technique was later introduced in the United States by Morrow (1941) under the name ‘‘ratiodelay study.’’ The technique did not gain wide acceptance at the outset. In 1952 the name ‘‘work sampling’’ was coined by Brisley and Waddell. At that time increased attention was being paid to indirect labor. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 7 Work sampling Characteristics Simple method, that provides information fast and at considerably less cost Results are representative Can be adapted to analyze complex and sophisticated patterns of work Many work systems (5-50) can be included in the study Results are effective for determining machine and personnel utilization, and allowances applicable to the job and production standards. Particularly useful for analyzing non-repetitive or irregularly occurring activities where no complete methods or frequency descriptions are available Also called activity sampling, ratiodelay study, random observation method, snap-reading method, and observation ratio study Salvendy 2001 REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 8 Work sampling Advantages Comprehension of a large amount of workstations is possible Less time-consuming in comparison to the stop watch time study No special measuring instruments necessary Eliminates tension caused by constant observation of the worker Does not require continuous observations over a long period of time Represents typical or average conditions over a period of time where conditions change from hour to hour or day to day Ideally suited to studies of machine utilization, activity analyses, and delays Bruder 2012 Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 9 Work sampling Disadvantages Time-influencing variables and reasons for actual times are not directly apparent from the results of the study Requires the observer to identify and classify a wide range of work activities and delays Assumes that the worker uses an acceptable and standard method Results are based on non-recurring observations and thus are not to be verified later on Results may be manipulated by observing persons Performance rates can not be measured Bruder 2012 Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 10 Implementation of work sampling Reliability The accuracy of the data determined mainly depends on The number of observations made The length of the period under which the study was undertaken The conditions under which the study was conducted Reliability and accuracy of information can only be obtained by using a sufficiently large sample size and a sampling period representing typical conditions. To observe all possible conditions, several tour plans are worked out, and at the beginning of the observation one tour is chosen randomly. The observation tours are done, until the required amount of notations is achieved. The required amount of notations results from the desired statistical reliability of the results. In general, a confidence level of 95% is chosen. Salvendy 2001 REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 11 Implementation of work sampling Duration Work sampling studies normally extend over a long period (two- to four-week period) to enable a comparatively large number of observations at random intervals to be taken. “One-day work sampling studies” are useless, since they can not cover seldom occurring events. The recording can be interrupted and continued at a later time without consequences for the result. With intermediate evaluations, the achieved statistical quality of the results can be assessed. If it is sufficient, the study can be early stopped. Salvendy 2001 REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 12 Implementation of work sampling External or self-recording In general notations are done by observers (external recording) moving on their defined tour. Self-recording is possible, if technical aids (software) are provided and the statements to be noted are related to the task of the employees. Self-recording does not require additional personnel effort for observers, and is useful for activities, that are difficult to observe (e.g. designing) The decision for external or self-recording needs to be done prior to the start of the study. REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 13 Implementation of work sampling Work council If the observed activities shall be used for performance standards, or if they can be used to assess the performance of employees, the implementation of the study needs to be discussed with the work council prior to starting the study. REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 14 Implementation of work sampling Characteristic Content Example Representativeness of results Data represent a real situation Utilization of production facilities; effort for distinct tasks Randomness of data recording Every event must have the same chance to be recorded Observation tours with randomly chosen times and orders Effectiveness Implementation with 5-50 work systems is possible; software support allows studies on several events with several observers and durations of some weeks Recording of frequency of executed tasks simultaneously in different business areas without disturbance of the employees Reliability The reliability of the study can be ensured by statistics Statistical demands on the result determine the amount of notations Accuracy Results are as accurate as required Accuracy can be defined Requirements Qualified planning; no special professional demands on the implementation Observation rounds (amount, order, duration) Implementation Appropriate planning; interruption does not affect the results Several people can observe; absence or replacement of an observer does not affect the result REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 15 REFA standard program work sampling 1 Goal determination 2 Definition of activities to record 3 Preparation of notations External (E) or selfrecording (S)? E S 4 Tour planning: jobs, routes, times 4 Employee training 5 Technical/organizational preparation 5 Technical/organizational preparation 6 Test rounds and notations 6 Test rounds and notations 7 Evaluation of test tours 7 Evaluation of test tours 8 Continuation of notations 9 Intermediate evaluation Yes Confidence interval sufficient? 10 Final evaluation No REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 16 REFA standard program work sampling REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 17 Goal determination Applications of the study Gaining information on order throughput (execution and interruption times, actual throughput times) and to be executed tasks (frequency, occurrence, duration) Gaining information on working conditions (hazards and emissions) Determination of work data for performance standards and agreements Determination and checking of allowances Determination and display of shares of value-creating and nonvalue-creating activities REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 18 Goal determination Possible focusses of the study Production facilities: Utilization and interruption of utilization Do the machines operate at full capacity? For which tasks are they mainly used? What are the proportions of these machine utilization types? What are the ratios of fault and idle times of the machines? Working person: Activities and interruption of activities Do the workers operate at full capacity? Which activities are done by the workers and what are their time shares? Which allowance and waiting time proportions for the workers should be expected? Workpiece: Processing and interruption of processing Which processing steps need which time share? What is the ratio of the processing time (time actually worked on the work piece) to the throughput time (time it takes to produce it)? Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 19 Goal determination Corresponding to the goal of the study the following items are defined Study task and purpose Study area (business field, orders, processes, work systems) Time frame of the study Participants of the study Further preparations Decide on the recording form and the use of software Inform and train (in case of self-report) all participants REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 20