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Time Study Method

Time Study Method. Step 1 ... Selecting Work Elements Step 2 ... Timing the Elements Step 3 ... Determining Sample Size Step 4 ... Setting the Standard. Definite starting and stopping points Correspond to a standard work method. Analyst times a worker Continuous method Snap-back method

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Time Study Method

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  1. Time Study Method • Step 1 ... Selecting Work Elements • Step 2 ... Timing the Elements • Step 3 ... Determining Sample Size • Step 4 ... Setting the Standard

  2. Definite starting and stopping points Correspond to a standard work method Analyst times a worker Continuous method Snap-back method “ Irregular occurance “ Select time (t) Step 1 Step 2Selecting Work Elements Timing the Elements

  3. Step 3 ... Determining Sample Size 1/2 • Average time estimateclose to true long range average • n = [(z/p)(σ/t)]² • n = required sample size • p = precision of the estimate as a proportion of the true value • t = select time for a work element (w.e.) • σ = standard deviation of representative observed times for a w.e. • z = number of normal standard deviation needed for the desired confidence • Fallbeispiel: Workelement Standard deviation Select Time Sample Size Get two cartons 0.0305 0.50 5 Put liner in carton 0.0171 0.11 10 Place cups in cart. 0.0226 0.71 10 Seal carton 0.0241 1.10 10

  4. Step 3 ... Determining Sample Size 2/2 Sample size of each Work Element • Work Element 1 n = [(1.96/0.04) (0.0305/0.500)]² = 9 • Work Element 2 n = [(1.96/0.04) (0.0171/0.11)]² = 58 • Work Element 3 n = [(1.96/0.04) (0.0226/0.71)]² = 3 • Work Element 4 n = [(1.96/0.04) (0.0241/1.10)]² = 2

  5. Step 4 ... Setting the Standard 1/3 • Normal time for each work element NT = t(F)(RF) • Perfomance rating factor (RF) • Frequency of occurance (F) • Normal time for the cycle (NTC) NTC = ΣNT • Fallbeispiel: Workelement t F RF Get two cartons 0.53 0.50 1.05 Put liner in carton 0.10 1.00 0.95 Place cups in cart. 0.75 1.00 1.10 Seal carton 1.08 1.00 0.90

  6. Step 4 ... Setting the Standard 2/3 Normal Times of each Work Element • Work Element 1 NT1 = 0.53(0.50)(1.05) = 0.28 minute • Work Element 2 NT2 = 0.10(1.00)(0.95) = 0.10 minute • Work Element 3 NT3 = 0.75(1.00)(1.10) = 0.83 minute • Work Element 4 NT4 = 1.08(1.00)(0.90) = 0.97 minute Total = 2.18 minutes

  7. Step 4 ... Setting the Standard 3/3 • Allowance Time: ST = NTC(1 + A) • Standard time for the coffee cup packaging operation Solution for A = 0.15 ST = 2.18(1 + 0.15) = 2.51 minutes/carton Production standard for eight-hour day (480 minutes/day) / (2.51 minutes/day) = 191 cartons/day • Overall Assessment of Time Study • Not useful for tasks that are different each time • Inexperienced persons should not conduct time studies • Subjectivity is involved • BUT: Conducted by experienced observers  satisfactory tool for setting equitable time standards

  8. 3 Methods • Elemental Standard Data Approach • Predetermined Data Approach • Work Sampling

  9. Elemental Standard Data Approach-- Highlights -- • Decreases the number of time studies • Time studies are saved as elemental standard datain a database • Define other job standards • Job standards before production begins

  10. Elemental Standard Data Approach-- Attention! -- • Does not eliminate time studies! • Check new job standards from time to time (gap between theory an reality). • Not the best method

  11. Predetermined Data Approach • No time studies. • Micromotionsinstead of work elements • Time unit for a micromotion is Time Measurement Unit (TMU) 1 TMU = 0.0006 minute = 36ms • Get TMUs from public databases (i.e. Methods Time Measurement (MTM)-databases like MTM-1). Basic micromotions in MTM-1 are reach, move, position, turn, release,…

  12. Predetermined Data Approach-- Steps to the job standard -- • Divide each work element into micromotions • Find a database for the micromotions’ values (TMUs, factors,…) • Sum up the normal times for each micromotion (= normal time) • Calculate the standard time with the normal time and the allowances (factors, constant values).

  13. Predetermined Data Approach-- Example -- A worker has to move an 18 pound object to an exact location 20 inches away.

  14. 1.11 * Predetermined Data Approach-- Table 1 – MTM predetermined Data for the Move Micromotion -- 22.1 + 3,9 = 28 TMUs

  15. Predetermined Data Approach++ • Job standards before production begins • Compare work methods without time studies • Consistency in setting time standards (i.e. no recording errors from time studies) • Biased judgment is eliminated • No time studies

  16. Predetermined Data Approach-- • Dividing work element into micromotions • Impractical for products and services with low repeatability • Micromotions may not fit exactly to the work • Not all data are in the databases (i.e. the shape of an object). • The sum of the micromotions may not fit to the time really needed for the job (gap between theory and reality) • Misuse of the method

  17. Work Sampling Method-- Goals/Possibilities -- • Time which is needed for a specific activity by a worker or machine. • Effectiveness of machines or workers • Job content • Cost of jobs or activities • Allowance time for the 2 Methods above (i.e. resting time, fatigue,..)

  18. Work Sampling Method-- Procedure -- • Activities (what is going to be measured?) • Observation form • Length of the study • Sample size • Observation times • Observer schedule • Observe the activities and record the data • Additional sampling is required?

  19. Work Sampling Method-- defining activities -- Activities could be … • Producing a product or service • Doing paperwork • Waiting for instructions • Being idle

  20. Work Sampling Method-- sample size -- Estimate the proportion of time spent on a specific activity, which doesn’t differ from the true proportion by more than an error e. p ...... Sample proportion (number of positive divided by sample size) e …… maximum error in the estimate

  21. Work Sampling Method Binomial distribution of the sampling and a big sample size Approximation to a normal distribution to determine the sample size.

  22. Work Sampling Method-- sample size -- The sample size affects the degree of precision n …… sample size z …… number of standard deviations needed to achieve the desired confidence

  23. Work Sampling Method-- Example -- • Medical records storage and retrieval system • Determine Advisability of Purchase • Registered Nurses – RNs • Licensed Vocational Nurses – LVNs • Ward staffed by 8 RNs and 4 LVNs • Proportion of time spent accessing records

  24. Work Sampling Method-- Example -- • Time spent accessing records takes estimated about 20 % of RNs and 5 % of LVNs time • Requirement: 95 % Confidence that the estimate falls within + 0.03 of true proportion • Sample size ???

  25. Work Sampling Method-- Example -- • RN: • LVN:

  26. Work Sampling Method-- Example -- 8 RNs and 4 LVNs can be observed on each trip RNs: trips LVNs: trips  688 observations of RNs 344 observations of LVNs

  27. Work Sampling Method-- Example -- Results of the Initial Study

  28. Work Sampling Method-- Example -- • Annual amortization costs for the new system 150.000 $ (estimated) • System reduces time nurses spend accessing records by 25 % (estimated) • Total anual salary expense RNs 3.628.000 $ LVNs 2.375.000 $ • Nurses could use productively time saved by system

  29. Additional Sampling required ?? RNs 124  0.1802 LVNs 28  0.0814 Original estimates off the mark  sample size smaller FaultTolerance+ 0.03  between 0.15 and 0.21 Work Sampling Method-- Example --

  30. Work Sampling Method-- Example --

  31. Work Sampling Method-- Example -- • Net Savings: 0.25[(3.628.000$)(0.18) + (2.375.000$)(0.08)] - 150.000$ = 60.760$ • Worst Case 0.15 (RNs) & 0.05 (LVNs) • Net Savings 0.25[(3.628.000$)(0.15) + (2.375.000$)(0.05)] - 150.000$ = 15.737$

  32. Work Sampling Method-- Overall Assesment -- Advantages:  No special training required  No stopwatches needed  Simultaneous Studies  activities of groups, rather than individuals Major Disadvantage  Large number of brief observations

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