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Method for establishing employee productivity standards in which (1) a complex task is broken into small, simple steps, (2) the sequence of movements taken by the employee in performing those steps is carefully observed to detect and eliminate redundant or wasteful motion, and (3) precise time taken for each correct movement is measured. From these measurements production and delivery times and prices can be computed and incentive schemes can be devised. Generally appropriate only for repetitive tasks, time and motion studies were pioneered by the US industrial engineer Frederick Winslow Taylor (1856-1915) and developed by the husband and wife team of Frank Gilbreth (1868-1924) and Dr. Lillian Gilbreth (1878-1972). See also Taylorism.

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Time and motion study
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A time and motion study (or time-motion study) is a business efficiency technique combining the Time Study work of Frederick Winslow Taylor with the Motion Study work of Frank and Lillian Gilbreth (the same couple as is best known through the biographical 1950 film and book Cheaper by the Dozen). It is a major part of scientific management (Taylorism). After its first introduction, time study developed in the direction of establishing standard times, while motion study evolved into a technique for improving work methods. The two techniques became integrated and refined into a widely accepted method applicable to the improvement and upgrading of work systems. This integrated approach to work system improvement is known as methods engineering[1] and it is applied today to industrial as well as service organizations, including banks, schools and hospitals.[2]
Time and motion study have to be used together in order to achieve rational and reasonable results. It is particularly important that effort to be applied in motion study to ensure equitable results when time study is used. In fact, much of the difficulty with time study is a result of applying it without a thorough study of the motion pattern of the job. Motion study can be considered the foundation for time study. The time study measures the time required to perform a given task in accordance with a specified method and is valid only so long as the method is continued. Once a new work method is developed, the time study must be changed to agree with the new method.[3]

Contents [hide] * 1 Time study * 2 Criticisms * 3 Motion studies * 4 Taylor Vs. the Gilbreths * 5 Direct time study procedure * 6 Conducting time studies * 7 See also * 8 References * 9 External links |
[edit] Time study
Time study is a direct and continuous observation of a task, using a timekeeping device (e.g., decimal minute stopwatch, computer-assisted electronic stopwatch, and videotape camera) to record the time taken to accomplish a task[4] and it is often used when:[5] * there are repetitive work cycles of short to long duration, * wide variety of dissimilar work is performed, or * process control elements constitute a part of the cycle.
The Industrial Engineering Terminology Standard defines time study as "a work measurement technique consisting of careful time measurement of the task with a time measuring instrument, adjusted for any observed variance from normal effort or pace and to allow adequate time for such items as foreign elements, unavoidable or machine delays, rest to overcome fatigue, and personal needs."[6]
The systems of time and motion studies are frequently assumed to be interchangeable terms, descriptive of equivalent theories. However, the underlying principles and the rationale for the establishment of each respective method are dissimilar, despite originating within the same school of thought.
The application of science to business problems, and the use of time-study methods in standard setting and the planning of work, was pioneered by Frederick Winslow Taylor.[7] Taylor liaised with factory managers and from the success of these discussions wrote several papers proposing the use of wage-contingent performance standards based on scientific time study.[8] At its most basic level time studies involved breaking down each job into component parts, timing each part and rearranging the parts into the most efficient method of working.[9] By counting and calculating, Taylor wanted to transform management, which was essentially an oral tradition, into a set of calculated and written techniques.[10][11]
Taylor and his colleagues placed emphasis on the content of a fair day’s work, and sought to maximize productivity irrespective of the physiological cost to the worker.[12] For example, Taylor thought unproductive time usage (soldiering) to be the deliberate attempt of workers to promote their best interests and to keep employers ignorant of how fast work could be carried out.[13] This instrumental view of human behavior by Taylor prepared the path for human relations to supersede scientific management in terms of literary success and managerial application.
[edit] Criticisms
In response to Taylor’s time studies and view of human nature, many strong criticisms and reactions were recorded. Unions, for example, regarded time study as a disguised tool of management designed to standardize and intensify the pace of production. Similarly, individuals such as Gilbreth (1909), Cadbury[14] and Marshall[15] heavily criticized Taylor and pervaded his work with subjectivity. For example, Cadbury[16] in reply to Thompson[17] stated that under scientific management employee skills and initiatives are passed from the individual to management,[18] a view reiterated by Nyland.[19] In addition, Taylor’s critics condemned the lack of scientific substance in his time studies,[20] in the sense that they relied heavily on individual interpretations of what workers actually do.[21] However, the value in rationalizing production is indisputable and supported by academics such as Gantt, Ford and Munsterberg, and Taylor society members Mr C.G. Renold, Mr W.H. Jackson and Mr C.B. Thompson.[22]
[edit] Motion studies
In contrast to, and motivated by, Taylor’s time study methods, the Gilbreths proposed a technical language, allowing for the analysis of the labor process in a scientific context.[23] The Gilbreths made use of scientific insights to develop a study method based upon the analysis of work motions, consisting in part of filming the details of a worker’s activities while recording the time.[24] The films served two main purposes. One was the visual record of how work had been done, emphasising areas for improvement. Secondly, the films also served the purpose of training workers about the best way to perform their work.[25] This method allowed the Gilbreths to build on the best elements of these work flows and to create a standardized best practice.[26]
[edit] Taylor Vs. the Gilbreths
Although for Taylor, motion studies remained subordinate to time studies, the attention he paid to the motion study technique demonstrated the seriousness with which he considered the Gilbreths’ method. The split with Taylor in 1914, on the basis of attitudes to workers, meant the Gilbreths had to argue contrary to the trade unionists, government commissions and Robert Hoxie[27] who believed scientific management was unstoppable.[28] The Gilbreths were charged with the task of proving that motion study particularly, and scientific management generally, increased industrial output in ways which improved and did not detract from workers' mental and physical strength. This was no simple task given the propaganda fuelling the Hoxie report and the consequent union opposition to scientific management. In addition, the Gilbreths credibility and academic success continued to be hampered by Taylor who held the view that motion studies were nothing more than a continuation of his work.
While both Taylor and the Gilbreths continue to be criticized for their respective work, it should be remembered that they were writing at a time of industrial reorganization and the emergence of large, complex organizations with new forms of technology. Furthermore, to equate scientific management merely with time and motion study and consequently labor control not only misconceives the scope of scientific management, but also misinterprets Taylor’s incentives for proposing a different style of managerial thought.[29]
[edit] Direct time study procedure
Following is the procedure developed by Mikell Groover for a direct time study:[30] 1. Define and document the standard method. 2. Divide the task into work elements.
These first two steps are conducted prior to the actual timing. They familiarize the analyst with the task and allow the analyst to attempt to improve the work procedure before defining the standard time. 3. Time the work elements to obtain the observed time for the task. 4. Evaluate the worker’s pace relative to standard performance (performance rating), to determine the normal time.
Note that steps 3 and 4 are accomplished simultaneously. During these steps, several different work cycles are timed, and each cycle performance is rated independently. Finally, the values collected at these steps are averaged to get the normalized time. 5. Apply an allowance to the normal time to compute the standard time. The allowance factors that are needed in the work are then added to compute the standard time for the task.
[edit] Conducting time studies
According to good practice guidelines for production studies [31] a comprehensive time study consists of: 1. Study goal setting; 2. Experimental design; 3. Time data collection; 4. Data analysis; 5. Reporting.
The collection of time data can be done in several ways, depending on study goal and environmental conditions. Time and motion data can be captured with a common stopwatch, a handheld computer or a video recorder. There are a number of dedicated software packages used to turn a palmtop or a handheld PC into a time study device. As an alternative, time and motion data can be collected automatically from the memory of computer-control machines (i.e. automated time studies).
[edit] See also * Ergonomics * Human factors * Methods-time measurement * Predetermined motion time system * Standard time * -------------------------------------------------
Evolutionary economics
Time and Motion Study, Analysis Through Statistics
Higher productivity in organizations leads to national prosperity and better standard of living for the whole community. Improving productivity through time and motion study is used in the manufacturing sector and allied industries. Work study consists of two aspects method study and work measurement which when applied effectively results to higher productivity. This paper deals with the use of work measurement for rebar placement activity, studying the performance of workers and its analysis through statistics.

Puniavathi Puranam, M.E.Student
Prof. Pramila. R. Adavi, Civil Engg.Department MAEER’S MIT, Pune.
Introduction
Project cost and schedule performance depend largely on the quality of project planning, work area readiness preparation and the resulting productivity of the work process made possible in project execution. The construction industry sets in motion the process of economical growth in the country; investment in this sector contributes 6.5% of Gross Domestic Product (GDP) growth (Das, 2003). Every Rs.1 investment in the construction industry causes a Rs.0.80 increment in GDP as against Rs.0.20 and Rs.0.14 in the fields of agriculture and manufacturing industry, respectively. Statistics over the period have shown that compared to other sectors, this sector of economic activity generally creates 4.7 times increase in incomes and 7.76 times increase in employment generation potentiality. Statistics is defined as the scientific method for collecting organizing, summarizing, presenting and analyzing data as well as drawing valid conclusions and making reasonable decisions on the basis of such analysis. The three major functions where statistics can be found in major enterprise are: a. The planning of operations:- This relates to either special projects or to the recurring activities of a firm over a specified period of time. b. The setting up of standards:- Understanding the size of employment, volume of sales, fixation of quality norms for the manufactured product, norms of the daily output, and so forth. c. The function of control:- This involves comparison of actual production achieved against the norm or target set earlier. In case the production has fallen short of the target, it gives remedial measures so that such a deficiency does not occur again.
Work measurement techniques find the time required to do a job by a qualified operator working at a standard pace and using the standard method. The time in minutes or hours calculated is known as standard time. The commonly employed work measurement techniques are: * Stop Watch Procedure of Time Study * Predetermined Motion Time Systems * Synthesis-Synthesied Time Standards * Analytical Estimating * Work sampling
The study highlights the use of stop watch procedure of time study, work sampling for the rebar placement.
Time Study
Time study is a work measurement technique for recording the times and rates of working for the elements of a specified job carried out under specified conditions and for analyzing data so as to determine the time necessary for carrying out the job at a defined level of performance.
Essentials of Time Study * An accurate specification of where the job begins and where it ends, and the method by which it is carried out, including details of material, equipment. * A system of recording the observed times taken by workers to do the job while under observation.
Procedure of Time Study * Identifying the job to be timed and operations to be timed. * Obtaining an improved procedure from method study department. * Select worker for study * Collecting the equipment and arrange machinery required to conduct time study and ensure accuracy in recording time * Explaining to the worker the improved working procedure and use of tools and fixtures * Breaking the job into operations and operations into elements and writing them in a proper format * Conducting the observations and recording them on the time study form * Rating the performance of the worker
Applications of Time Study * For determining schedules and planning of work * For calculation of Standard costs and as an aid in preparing budgets * For determining machine effectiveness, the number of machines which one person can operate and also for construction activities.
Work Sampling
Work sampling is a work measurement technique in which a large number of instantaneous observations are made a random intervals over a specified period of time of group of workers machine and process of finding the percentage occurrence of a certain activity by statistical sampling.

Work sampling procedure can be divided in the following three phases:-

a) Preparing for work sampling
1) Statement of the main objective of the study, obtaining approval of the supervisor.
2) Establish quantitative measure of the activity, selection of training of personnel and making a detail plan for taking observations.

b) Performing work sampling
1) Describing and classifying the elements to be studied in details, designing the observation form and determining the number of days or shifts required for the study.
2) Developing properly randomized times of observations, observing activity and recording data, summarizing the data at the end of each day.

c) Evaluating and presenting results of work sampling.
1) Evaluate the validity and reliability of data, presenting, analyzing data and planning for future studies.

Uses of work sampling:-
1) determination of time standards and delay allowances
2) Aid in the measurement of overall performances
3) Job evaluation and manpower planning.
4) For appraisal of safety performance and organizational efficiency.
Case Study
Keeping the above technique in mind a residential project was taken up as a case study where data was collected from a G+7 apartment in Aurangabad, Maharashtra.
Work Sampling
Table1:- Workers Performance on rebar placement. Day-1 | | Workers:- | Visit No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | | 10:45 | IW | IW | IW | IW | IW | IW | IW | IW | | 10:55 | IW | IW | IW | IW | IW | IW | IW | IW | | 11:05 | IW | IW | IW | IW | IW | IW | IW | IW | | 11:20 | SW | SW | SW | SW | SW | SW | SW | SW | | 11:25 | SW | SW | SW | SW | SW | SW | SW | SW | | 11:32 | SW | SW | SW | SW | SW | SW | SW | SW | | 11:40 | SW | SW | SW | SW | SW | SW | SW | SW | | 11:48 | SW | SW | SW | SW | SW | SW | SW | SW | | 12:05 | SW | SW | SW | SW | SW | SW | SW | SW | | 12:15 | SW | SW | SW | SW | SW | SW | SW | SW | | 12:30 | SW | SW | SW | SW | SW | SW | SW | SW | | 12:45 | SW | SW | SW | SW | SW | SW | SW | SW | | 2:45 | IW | IW | IW | IW | IW | IW | IW | IW | | 2:55 | IW | IW | IW | IW | IW | IW | IW | IW | | 3:12 | IW | IW | IW | IW | IW | IW | IW | IW | | 3:27 | SW | SW | SW | SW | SW | SW | SW | SW | | 3:40 | SW | SW | SW | SW | SW | SW | SW | SW | | 4:00 | SW | SW | SW | SW | SW | SW | SW | SW | | 4:12 | SW | SW | SW | SW | SW | SW | SW | SW | | 4:25 | SW | SW | SW | SW | SW | SW | SW | SW | | 4:40 | SW | SW | SW | SW | SW | SW | SW | SW | |

6 days required for the placing of beams in proper location for 6th floor wing c. No. of workers on the working area:-8. Workers: - 1-5 are fitters, 6-8 are helpers. Table here shows the sample of 2 days of work sampling procedure. Day-2 | No. of workers on the working area:-10. Workers: - 1-5 are fitters, 6-10 are helpers. | | Workers:- | Visit no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 10:00 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 10:17 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 10:22 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 10:35 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 10:40 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 10:45 | SW | IW | DW | DW | IW | SW | SW | DW | DW | SW | 10:55 | SW | IW | DW | DW | IW | SW | SW | DW | DW | SW | 11:05 | SW | IW | DW | DW | IW | SW | SW | DW | DW | SW | 11:20 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 11:25 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 11:32 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 11:40 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 11:48 | DW | DW | DW | DW | IW | DW | DW | DW | DW | IW | 12:05 | DW | DW | SW | SW | IW | SW | SW | SW | SW | IW | 12:15 | IW | IW | SW | SW | SW | SW | SW | SW | SW | SW | 12:30 | IW | IW | IW | IW | IW | IW | IW | IW | IW | IW | 12:45 | IW | IW | IW | IW | IW | IW | IW | IW | IW | IW | 2:45 | SW | SW | SW | SW | SW | SW | SW | SW | SW | SW | 2:55 | SW | SW | SW | SW | SW | SW | SW | SW | SW | SW | 3:12 | SW | SW | SW | SW | SW | SW | SW | SW | SW | SW | 3:27 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 3:40 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 4:00 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 4:12 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 4:25 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 4:35 | DW | IW | IW | DW | DW | DW | DW | DW | DW | DW | 4:55 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 5:10 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 5:20 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 5:35 | DW | DW | DW | DW | DW | DW | DW | DW | DW | DW | 5:45 | DW | DW | DW | DW | DW | DW | DW | IW | DW | DW |

Category | Study Number | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Direct work | 60.02% | 71.27% | 61.75% | 71.22% | 68% | 70.53% | 70.08% | Essential contributory work. | 20.98% | 17.10% | 18.82% | 15.51% | 17.7% | 14.00% | 15.48% | Ineffective work | 19.0% | 11.63% | 19.43% | 13.27% | 14.3% | 15.47% | 14.44% |

The Table depicts work sampling used for measuring the performance of workers on rebar placement: - It consists of studies taken from 6th floor wing c, 7th floor wing a, b, c Roof level wing a, b, c.

Categories are further subdivided into narrowly defined categories of activity as follows: * Direct or Effective Work:-

1.Direct work—Place, align, force, and tie into position plus those Elements which contribute directly to completing the unit of work. * Essential Contributory Work :-

2. Obtain or transport tools and materials within immediate vicinity of work area including torch, sledge, wire cutters, rigging, reinforcement tie wire, etc. Also includes searching for materials. The immediate vicinity is defined as the existing concrete mat. The staging area is excluded.

3. Obtain or transport tools and materials outside of immediate vicinity of work area including all tool and material movement not in close proximity to the work location. Activities in the staging area are included.

4. Includes activities associated with crane deliveries until such time as the lift actually begins.

5. Receive/give instructions and read drawings involving instructions communicated to or by supervisors and among crew members. Casual talking is not considered instructions. Also included is the studying of drawings and planning work. Foreman in staging area looking for materials is considered as planning work.

6. Minor contributory work measuring or marking bar location, holding a bar to prevent movement, cutting w/torch, moving scaffolding, etc. * Ineffective Work:-

7. Travel empty-handed to and from the work area and within the work area, either on foot or in a vehicle.

8. Idle, unexplained waiting that cannot be accounted for. Distinction between idle and waiting for prerequisite activity or craft is if worker is in a position to assist, he is waiting for prerequisite work, otherwise, unexplained. Includes personal time while in the immediate vicinity of the work location.

9. Waiting for tools, materials, instructions, crane deliveries, prerequisite work, other crafts, etc. Workers should be in position to continue work when the delay ends.

10. No contact—failure to observe worker who is assigned to a specific work location. Includes early quit, late start, and time away from the immediate work location.
Conclusion
The optimum number of personnel for rebar placement is 10 - 12 on the work location. The optimum number of human resources assigned for construction activities leads to economy, reduction in time and quality work is obtained. Table 2:- TIME STUDY PROCEDURE USED FOR BEAMS. | Continuous time study: - 6th Floor WingC | Time required (secs) | Work location | Crew activity | 612.82 | B117 | Align, position, marking of stirrups. | 271.11 | B117 | Placing of stirrups | 556.23 | B117 | Tying of stirrups to top bars | 1160.63 | B117 | Placing of bottom bars and tying | 482.1 | B47,B48 | Align, position, marking of stirrups | 309.11 | B47,B48 | Placing of stirrups | 1339.26 | B47,B48 | Tying of stirrups to top bars | 1852.63 | B47,B48 | Placing of bottom bars and tying | 500.13 | B123 | Align, position, marking of stirrups | 198.74 | B123 | Placing of stirrups | 759.56 | B123 | Tying of stirrups to top bars | 1076.27 | B123 | Placing of bottom bars and tying | 733.62 | B38 | Align, position, marking of stirrups | 465.36 | B38 | Placing of stirrups | 653.26 | B38 | Tying of stirrups to top bars | 446.64 | B38 | Placing of bottom bars and tying | 441.36 | B84 | Align, position, marking of stirrups | 192.68 | B84 | Placing of stirrups | 563.65 | B84 | Tying of stirrups to top bars | 802.16 | B84 | Placing of bottom bars and tying | 553.23 | B72,73 | Align, position, marking of stirrups | 513.43 | B72,73 | Placing of stirrups | 753.26 | B72,73 | Tying of stirrups to top bars | 922.1 | B72,73 | Placing of bottom bars and tying | 620.32 | B119 | Align, position, marking of stirrups | 491.25 | B119 | Placing of stirrups | 685.36 | B119 | Tying of stirrups to top bars | 870.18 | B119 | Placing of bottom bars and tying |

Time study and work sampling applied for rebar placement show us that there was a lot of physical stress and strain for the essential contributory work, i.e. workers working manually. The stress and strain can be reduced by using the material handing lift on site for stirrups and cover blocks which reduces time, and effective time can be used for direct work. Bar cutting and bar bending machine on site helps in improvement of labour productivity.

The normal distribution, normal curve with respect to beams shows that the area under the curve for one standard deviation from the mean covers more than 68.27% area and area under the curve from mean for 2ó, 3ó covers 95.45%, 99.73%. The reasons for the above results is due to the alteration in the drawings, delay in payment and also change in the gang working on the work location from slab to slab. The results of the statistical analysis for the time study:- | Statictics using EXCEL Sheets | Activity a | Activity b | Activity c | Activity d | Mean | 566.99 | 366.41 | 740.36 | 976.67 | Standard Error | 33.00500 | 48.70055 | 89.77151 | 147.79122 | Mode | 0.00 | 0.00 | 0.00 | 0.00 | Median | 572.80 | 387.24 | 669.31 | 896.14 | StandardDeviation | 93.352 | 137.75 | 253.93 | 418.02 | Sample Variance | 8714.6 | 18974 | 64481 | 174738 | Kurtosis | -0.6248 | -1.7164 | 2.1486 | 0.6224 | Skewness | 0.3744 | -0.1782 | 1.8667 | 1.0420 | Range | 292.26 | 320.75 | 783.03 | 1405.99 | Minimum | 441.36 | 192.68 | 556.23 | 446.64 | Maximum | 733.62 | 513.43 | 1339.3 | 1852.6 | Sum | 4535.9 | 2931.2 | 5922.8 | 7813.4 | Count | 8 | 8 | 8 | 8 | Correlation Coefficient | r 12 | 0.6419 | ------ | ----- | ------ | r 13 | -0.3570 | ---- | ---- | ----- | r 14 | -0.5541 | ---- | ---- | ----- | r 23 | -0.0762 | ---- | ----- | ---- | r 24 | -0.4071 | ---- | ----- | ---- | r 34 | 0.8243 | ----- | ----- | --- | Partial correlation coefficients | r12.34 | 0.5220 | ----- | ----- | ----- | r13.24 | -0.0869 | ----- | ------ | ----- | r14.23 | -0.1493 | ---- | ----- | ----- |

The onsite training programs for the operators and personnel should be conducted. Motivation and job evaluation through questionnaires can be used in finding the best way for performing the activities. Checklist for different construction activities reduces time and improves the efficiency of workers.

Rebar placement and installation

Work Study and study of ergonomics can be used for developing better incentive schemes and safety measures. The study on occupational and health safety and working conditions is a must. Use of statistics through softwares reduces time, the samples of different construction activities can be evaluated and graphs interpretated in an efficient manner, thus improving the quality of construction as well as improving the working conditions of the workers on site. The factors which effect the labour productivity are material shortages, delay in inspection, payment delay, alteration in drawings and specification during execution, tool / equipment shortages etc.
References
1. H. Randolph Thomas (1991) Labor Productivity and work sampling the bottom line, J.Cons. Eng. Management., p.p-423-444. 2. Md. Salim and Leonhard E. Bernold, (1993) Effects of design-Integrated process Planning on productivity in rebar placement. J. Constr. Eng. Management p.p-720-738. 3. Fwu-Shiun Liou1 and John P. Borcherding (1986) Work sampling can predict Unit Rate of productivity, J.Constr. Eng. Management p.p 90-103. 4. H. Randolph Thomas, Jeffrey Daily, (1983) Crew performace measurement via Activity sampling J. Cons. Engg. Management p.p 309-320. 5. Adnan Enshassi, Sherif Mohamed, Ziad Abu Mustafa1 and Peter Eduard Mayer (2007) Factors affecting labour productivity in building projects in the Gaza strip. J. of Civil Engg and Management .p245-254 6. O.P. Khanna, Work Study, Dhanpat Rai Publications. 7. M.N.Pal, A.K.Chatterjee Indian Adaptation Introduction to Work Study. International Labour Office, Geneva 8. Marvin E.Mundel, Motion and Time study improving productivity, Prentice Hall India. 9. G.C.Beri Business Statistics Tata Mc Graw Hill. 10. Murray R.Spiegel, Larry J Stephens, Adapted by Narinder Kumar Schaum’s outlines Statictics. Tata McGraw Hill Publication.
NBMCW May 2012