department of industrial engineering allowance and time...

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Islamic University of Gaza - Palestine

Department of Industrial Engineering

Allowance and Time Study


Time Study and Work Measurement

Normal Performance• A pace of working that can be maintained by a properly trained

average worker throughout an entire work shift withoutdeleterious short-term or long-term effects on the worker’shealth or physical well-being– Normal performance = 100% performance– Common benchmark of normal performance:

• Walking at 3 mi/hr

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Performance Rating• Analyst judges the performance or pace of the worker relative

to the definition of standard performance used by theorganization– Standard performance Pw = 100%

• Slower pace than standard Pw < 100%• Faster pace than standard Pw > 100%

– Normal time Tn = Tobs(Pw )



Normal Time• The time to complete a task when working at normal

performance

Tn = Tobs(Pw )

where Tobs = observed time, Tn = normal time, and Pw =worker performance or pace




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Example: Normal Performance• Given: A man walks in the early morning for health and

fitness. His usual route is 1.85 miles. A typical time is 30 min.The benchmark of normal performance = 3 mi/hr.

• Determine: (a) how long the route would take at normalperformance and (b) the man’s performance when hecompletes the route in 30 min.



(a) At 3 mi/hr, time = 1.85 mi / 3 mi/hr= 0.6167 hr = 37 min

(b) Rearranging equation, Pw = Tn / Tc

Pw = 37 min / 30 min = 1.233 = 123.3 %




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Reasons for Lost Time at Work

Work-related interruptions

• Machine breakdowns• Waiting for materials or parts• Receiving instructions from foreman• Talking to co-workers about work-related matters• Rest breaks for fatigue• Cleaning up at end of shift

Non-work-related interruptions

• Personal needs (e.g., restroom breaks)• Talking to co-workers about matters unrelated to work• Lunch break• Smoke break• Beverage break• Personal telephone call




How to Allow for Lost Time• Two approaches used by companies:

1. Scheduled rest breaks during the shift• Typical - one 15-minute break in mid-morning and another in mid-

afternoon2. A PFD allowance is added to the normal time

n This allows the worker to take a break on his/her own time




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PFD Allowance• Personal time

– Rest room breaks, phone calls, water fountain stops, cigarettebreaks (5% typical)

• Fatigue– Rest allowance to overcome fatigue due to work-related stresses

and conditions (5% or more)• Delays

– Machine breakdowns, foreman instructions (5% typical)



Allowances in Time Standards• Normal time is adjusted by an allowance factor Apfd to obtain

the standard time• Purpose of allowance factor is to compensate for lost time

due to work interruptions and other reasons




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Standard Time• Defined as the normal time but with an allowance added in to

account for losses due to personal time, fatigue, and delaysTstd = Tn (1 + Apfd)

where Tstd = standard time, Tn = normal time, and Apfd = PFDallowance factor

where pfd = personal time, fatigue, and delays

• Also called the allowed time



Standard Performance• Same as normal performance, but acknowledges that periodic

rest breaks must be taken by the worker– Periodic rest breaks are allowed during the work shift– Other interruptions and delays also occur during the shift




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Normal Time =(Total Time) (% of time working) (Rating)

Number of units Produced

Standard Time = Normal Time1 - Allowance

Work Sampling Equations


• Labor standards are based on observing worker doing task– Observe only a sample of work– Use average time & pace to set standard

• Disadvantages– Requires a trained & experienced analyst– Standard cannot be set before task is performed

Time Studies




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The Eight Steps to Conducting a Time Study

ÊDefine the task to be studied (after a methods analysis)Ë Break down the task into precise elementsÌ Decide how many times each element of the task must be

measuredÍ Record the times and ratings of performance for

the task elementsÎ Compute the average observed cycle time (element times

adjusted for unusual influences)


ÏCompute the normal time for each task element:Normal time = (Average actual cycle

time) x (Rating factor)ÐSum the normal times for each element to develop a

total normal time for the taskÑCompute the standard time:

The Eight Steps to Conducting a Time Study – cont.)

Standard time = Total normal time1- Allowance factor




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Allowances

• Personal time allowance - 4% - 7% of total time - use of restroom, water fountain, etc.

• Delay allowance - based upon actual delays that occur

• Fatigue allowance - to compensate for physical or mental strain, noise level, tediousness, heat and humidity, assumption of an abnormal position, etc.


Allowances

• Allowances refers to extra time allowed, beyond completion of the task itself

• Some allowances are necessary for health and long term efficiency (like rest breaks),

• Others are pragmatically necessary, (like time for picking up dropped tools or consulting with supervisor)




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• Many jobs require human effort, and some allowance must be made for recovery from fatigue for relaxation.

• Allowance must also be made to allow a worker to attend to personal needs; and other allowances (e.g. contingency allowances) may also have to be added to the basic time in order to give the work content.

• The difficulty experienced in preparing a universally accepted set of exact allowances that can be applied to every working situation anywhere in the world is due to various reasons. The most important among them are:

– Factors related to the individual. If every worker in a particular working area were to be considered individually, it might well be found that a thin, active, alert worker at the peak (top) of physical condition required a smaller allowance to recover from fatigue than a fat, incompetent (unskilled) worker.

Allowances


– Factors related to the nature of the work itself. Many of the tables developed for the calculation of allowances give figures which may be acceptable for light and medium work in industry but which are inadequate when applied to operations involving very heavy and exhausting work. (i.e., furnaces in steel mills).

• Examples of these factors are: whether a worker has to perform the work standing up or sitting down, and position during work; whether force has to be used to move or carry loads from one place to another; whether the work itself results in excessive eye or mental strain, and so on.

– Factors related to the environment. Particular relaxation allowances, have to be determined with due regard to various environmental factors such as heat, humidity, noise, dirt, vibration, lighting intensity, dust, wet conditions, etc.

• Each of these will affect the amount of relaxation allowances needed.

Allowances




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• Relaxation allowances (which are intended to assist recovery from fatigue) are the only essential part of the time added to the basic time.

• Other allowances, such as contingency, policy and special allowances are applied under certain conditions only.

• Relaxation allowance is an addition to the basic time intended to provide the worker with the opportunity to recover from the physiological and psychological effects of carrying out specified work under specified conditions and to allow attention to personal needs.

• The amount of allowance will depend on the nature of the job.

Calculation of allowances





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Ra are calculated so as to allow the worker to recover from fatigue.

Fatigue may be defined as a physical and/or mental weariness, real or imagined, existing in a person and harmfully affecting the ability to perform work. The effects of fatigue can be lessened by rest pauses, during which the body recovers from its effort.

• Allowances for fatigue are normally added element by element to the basic times, so that a work value for each element is built up separately, the element standard times being combined to give way the standard time for the whole job or operation.

• In this way it is possible to deal with any extra allowance which may be required to compensate for severe climatic conditions, since the element may sometimes be performed in cool weather and sometimes when it is very hot.

Relaxation allowances (Ra)


Fixed allowances and variable allowances.

Fixed allowances are composed of:

• Allowances for personal needs. This allowance provides for the necessity to leave the workplace to attend to personal needs such as washing, going to the bathroom or getting a drink.

• Common figures applied by many enterprises range from 5 to 7 per cent.

• Allowances for basic fatigue. This allowance, always a constant, is given to take account of the energy expended while carrying out work and to lessen monotony.

• A common figure is 4 per cent of basic time. This is considered to be sufficient for a worker who carries out the job while seated, who is engaged on light work in good working conditions.

Relaxation allowances components




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Variable allowances are added to fixed allowances when working conditions differ noticeably from those stated above, for instance because of poor environmental conditions that cannot be improved, added stress and strain in performing the job in question, and so on.

• Relaxation allowances are given as percentages of the basic time. They are normally calculated on an element-by-element basis.

Rest pauses

• Relaxation allowances can be taken in the form of rest pauses. While there is no hard and fast rule governing rest pauses, a common practice is to allow a 10 to 15 minute break at mid-morning and mid-afternoon.

Variable allowances


• They break up the monotony of the day.

• They give workers the chance to recover from fatigue and to attend to personal needs.

• They reduce the amount of time off taken by workers during working hours.

• Where workers are working in conditions of heat, cold, noise or vibration it may be necessary to introduce mandatory rest pauses as part of a work-rest routine to ensure the health and safety of the workers.

Rest pauses are important for the following reasons




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• It is sometimes necessary to include allowances other than relaxation allowances in the compilation of standard time.

Contingency allowances• A contingency allowance is a small allowance of time which may be included in

a standard time to meet reasonable and expected items of work or delays.

• The exact measurement of which is uneconomical because of their rare or irregular occurrence

• Contingency allowances should not be greater than 5 per cent, and should only be given in cases where the study person is absolutely satisfied that the contingencies cannot be eliminated and that they are justified.

Other allowances


Special allowances

• Special allowances may be given for any activities which are not normally part of the operation cycle but which are essential to the satisfactory performance of the work.

• Such allowances may be permanent or temporary; wherever possible, these allowances should be determined by time study.

Other allowances




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Start-up allowance to compensate for time taken by any work and any enforced waiting time which necessarily occurs at the start of a shift or work period before production can begin.

A shut-down allowance may be given for work or waiting time occurring at the end of the day.

A cleaning allowance is given when the worker has to give attention from time to time to cleaning his machine or workplace.

Tool allowance is an allowance of time to cover the adjustment and maintenance of tools.

Some allowances are normally given per occasion or per batch. Such allowances are;

Set-up allowance, given to cover the time required for preparing a machine or process for production, an operation which is necessary at the start of production on a batch of fresh products or components.

Dismantling allowance may be given, to cover the time needed for making alterations to machine or process settings after completing a run of production.

Other allowances (cont.)


Reject allowance may be included in a standard time when the production of a proportion of defective products is inherent in the process, but is perhaps more usually given as a temporary addition to standard times, per job or per batch, if an occasional bad group of material has to be worked.

Learning allowances may be given to trainee operators engaged on work for which standard times have been issued, as a temporary benefit while they develop their ability.

Training allowance is a similar allowance given to an experienced worker to compensate for the time he is required to spend instructing a trainee, while both are working on jobs for which standard times have been set.

Implementation allowance, given to workers asked to adopt a new method or process to encourage them to attempt an enthusiastic implementation of the new ways.

Small batch allowance is required to allow a worker working on small batches to decide what to do and how to go about it and then to work up to a standard performance by practice and repetition.

Other allowances (cont.)




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Example

• Given: A direct time study was taken on a manual workelement using the snapback method. The regular cycleconsisted of three elements, a, b, and c. Element d is anirregular element performed every five cycles.Work element a b c dObserved time (min) 0.56 0.25 0.50 1.10Performance rating 100% 80% 110% 100%

• Determine(a) normal time(b) standard time for the cycle using Apfd=0.15


Solution

(a) Normal time:Tn = 0.56(1.00) + 0.25(0.80) + 0.50(1.10)

+ 1.10(1.0)/5 = 1.53 min

(b) Standard time:Tstd = 1.53(1 + 0.15) = 1.76 min




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RATING

Normal Pace

During the time study, the observer will rate the worker, that is, determine the adjustment to convert the observed time to a time that a normal, experienced worker would take

APL = MPL - Expectancy, (Acceptable Productivity Level, Motivated Productivity Level)


MPL (Motivated Productivity Level):

The work pace of a motivated worker possessing sufficient skill and effort to do the job, physically fit to do the job after adjustment to it, and working at an incentive pace that can be maintained day after day without harmful effect.

RATING




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Acceptable Productivity Level (APL): The work pace established by management or jointly by management and labor at a level that is considered satisfactory; it is established at a given relationship to motivated productivity level.

Expectancy is the expected level of productivity, it is also related to allowance. If allowance is low, expectancy discount tends to be high and vice-versa.

RATING


RATING TECHNIQUES

•There cannot be a set method to rate as different tasks within an activity requires different levels of skills and ways

•All tasks cannot be rated at a same scale




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RATING TECHNIQUES

Pace Rating:

The observer estimates the speed and concentrate on dynamic micromotions such as reach or move rather than stationary like position and grasp.

Objective Rating: (three steps)

• The observer rates the speed

• Observer estimates the task difficulty

• Task difficulty factor is multiplied by thespeed to get actual pace.


•Divide the elements and take multiple readings

•Categorize mental, fine manipulative and muscular jobs

•Categorize skilled, unskilled and semi skilled labor

•Categorize time of the day

•Rating is a very specialized task and enough training via videotapes, practice tests, different paces etc. should be carried out before actual assignment

RATING TECHNIQUES




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Computing Standard Times

• A standard time is a combination of:– The time it takes to complete a task– Allowances.

• This approach recognizes that it is not possible to work at top efficiency all day, all the time.


Methods for computing standard times

• rest.ST = NT + NT x allowance

= NT (1 + allowance)• Method 2: Compute allowances as a % of task time.

ST = NT / (1 – allowance)

ST = Standard Time: the time in which you expect workers to complete an operation.NT = Normal Time: time required to complete an operation for a given operatorOT = Mean Observed Time to complete an operation (from time study).

For an experienced operator who works at a 100% rate (R), OT = NT, andNT = OT x R/100 where R = the performance rating of the operator.




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Example: Method 1

• Suppose that your time study shows that it takes 3.5 minutes on average to complete a task. Rule of thumb for manual tasks: 15% allowances.

ST = NT + (NT * allowance)= 3.5 min + (3.5 min * .15)= 3.5 min + 0.525 min= 4.03 minutes.

Experienced operators will be expected to complete the task in this time.


But how can you estimate allowances?

• Observe foreign elements – what percentage of total time do they comprise?

• Methods for calculating allowances:– For personal needs,– For fatigue reduction




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Next, identify possible sources of fatigue

• Abnormal posture,• Muscular force,• Ventilation,• Lighting, • Visual strain • Mental strain, • Etc.


Question

• Does it make sense to estimate:– Allowances– Standard time– Efficiency for a cashier who may spend much time waiting for

customers to arrive?




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How should Standard Times be used to Evaluate and Motivate People?

• What happens when you set up a reward system? – All jobs have same standard time, but some are more

difficult,– Busy-time often results in slower production because you

are exceeding capacity,• Do you always get the behavior you expect?


Some insights

• The statistical accuracy of the time data increases withmore observations– Spend more time in analyzing important tasks; high

production operations

• Shorter work cycles allow more cycles to be timed.

• Tradeoff: Accuracy and precision vs. cost




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Performance Rating (leveling)

• Analyst observes and rates the worker’s performance relativeto the definition of standard performance

• The most difficult and controversial step in direct time study– Potential conflict of interest between the worker and the analyst

• Most common performance rating method is based on speed orpace

• Elemental rating vs. overall rating– If the work cycle is relatively short (less than 1 minute) and the work

content is similar throughout the cycle, then rating the entire cycle (overallrating) makes sense

– Otherwise elemental rating is more appropriate.


Chracteristics of a Good Rating System

• Consistency among tasks– A worker who can perform at 125% on one task should be able to do the

same on other tasks

• Consistency among analysts

• Easy to explain and easy to understand

• Based on a well-defined concept of standard performance

• Observe several cycles and different workers before rating

• Rate performance during the observation

• Worker notification




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Apply Allowances

• A PFD allowance is added to the normal time to computethe standard time

Tstd = Tn(1 + Apfd)

where Apfd = allowance factor for personal time, fatigue,and delays

• The function of the allowance factor is to inflate the valueof standard time in order to account for the variousreasons why the worker loses time during the shift


Rest Allowances

þ Personal time allowanceþ 4% - 7% of total time for use of restroom, water

fountain, etc.þ Delay allowance

þ Based upon actual delays that occurþ Fatigue allowance

þ Based on our knowledge of human energy expenditure




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Rest Allowances

11.. Constant allowance(A) Personal allowance ……………... 5(B) Basic fatigue allowance ………… 4

2. Variable allowances:(A) Standing allowance ……………… 2(B) Abnormal position

(i) uncomfortable (bending) ………… 2(ii) Very awkward (lying,

stretching) …………………… 7


Rest Allowances

(C) Use of force or muscular energy in lifting, pulling, pushingWeight lifted (pounds)20 …………………………………… 340……………………………………. 960……………………………………. 17

(D) Bad light:(i) Well below recommended…. 2(ii) Quite inadequate……………. 5




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Rest Allowances

(E) Atmospheric conditions (heat and humidity) …………… 0-10

(F) Close attention:(i) Fine or exacting……………….. 2(ii) Very fine or very exacting…… 5

(G) Noise level:(i) Intermittent—loud…………….. 2(ii) Intermittent—very loud

or high-pitched………………... 5


Rest Allowances

(H) Mental strain:(i) (i) Complex or wide span

of attention.…………………….. 4(ii) Very complex………………….. 8

(I) Tediousness:(i) Tedious…………..……………… 2(ii) Very tedious.…………………… 55




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Time Study Example S1

Average observed time = 4.0 minutesWorker rating = 85%Allowance factor = 13%

Normal time = (Average observed time) x (Rating factor)= (4.0)(.85)= 3.4 minutes

Standard time = = =Standard time = = =Normal timeNormal time1 1 -- Allowance factorAllowance factor

33..441 1 -- ..1313

33..44..8787

= = 33..99 minutesminutes


Example

Allowance factor Allowance factor = = 1515%%

PerformancePerformanceJob ElementJob Element 11 22 33 44 55 RatingRating

(A)(A) Compose and type letterCompose and type letter 88 1010 9 9 2121** 1111 120120%%(B)(B) Type envelope addressType envelope address 22 33 2 2 1 1 33 105105%%(C)(C) Stuff, stamp, seal, andStuff, stamp, seal, and 22 11 55** 2 2 11 110110%%

sort envelopessort envelopes

Cycle Observed (in minutes)Cycle Observed (in minutes)

1.1. Delete unusual or nonrecurring observations (marked with *)Delete unusual or nonrecurring observations (marked with *)2.2. Compute average times for each elementCompute average times for each element

Average time for A Average time for A = (= (8 8 + + 10 10 + + 9 9 + + 1111)/)/4 4 = = 99..55 minutesminutesAverage time for B Average time for B = (= (2 2 + + 3 3 + + 2 2 + + 1 1 + + 33)/)/5 5 = = 22..22 minutesminutesAverage time for C Average time for C = (= (2 2 + + 1 1 + + 2 2 + + 11)/)/4 4 = = 11..55 minutesminutes




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Example

3.3. Compute the normal time for each elementCompute the normal time for each element

Normal time for A Normal time for A = (= (99..55)()(11..22) = ) = 1111..44 minutesminutesNormal time for B Normal time for B = (= (22..22)()(11..0505) = ) = 22..3131 minutesminutesNormal time for C Normal time for C = (= (11..55)()(11..1010) = ) = 11..6565 minutesminutes

Normal time = (Average observed time) x (Rating)Normal time = (Average observed time) x (Rating)

4.4. Add the normal times to find the total normal timeAdd the normal times to find the total normal time

Total normal time Total normal time = = 1111..40 40 + + 22..31 31 + + 11..65 65 = = 1515..3636 minutesminutes


Example

5.5. Compute the standard time for the jobCompute the standard time for the job

Standard time =Standard time =Total normal timeTotal normal time

1 1 -- Allowance factorAllowance factor

= = = = 1818..0707 minutesminutes1515..36361 1 -- ..1515




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Work Sampling

þ Estimates percent of time a worker spends on various tasks

þ Requires random observations to record worker activity

þ Determines how employees allocate their timeþ Can be used to set staffing levels, reassign duties,

estimate costs, and set delay allowances

Islamic University of Gaza - PalestineWork Sampling

þ Advantages of work samplingþ Less expensive than time studyþ Observers need little trainingþ Studies can be delayed or interrupted with little

impact on resultsþ Worker has little

chance to affect results

þ Less intrusive




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þ Disadvantages of work samplingþ Does not divide work elements as completely as

time studyþ Can yield biased results if observer does not

follow random patternþ Less accurate, especially when

job element times are short

Work Sampling


1. Take a preliminary sample to obtain estimates of parameter values

2. Compute the sample size required3. Prepare a schedule for random observations at

appropriate times4. Observe and record worker activities5. Determine how workers spend their time




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Determining the sample size

n =n =zz22 pp((1 1 -- pp))

hh22

where n = required sample sizez = standard normal deviate for

desired confidence levelp = estimated value of sample

proportionh = acceptable error level in percent

Islamic University of Gaza - PalestineWork Sampling Example

Wants employees idle 25% of the timeSample should be accurate within 3%Wants to have 95.45% confidence in the resultsresults

n =n =zz22 pp((1 1 -- pp))

hh22

wherewhere nn == required sample sizerequired sample sizezz == 22 for a for a 9595..4545%% confidence levelconfidence levelpp == estimate of idle proportion estimate of idle proportion = = 2525% = .% = .2525hh == acceptable error of acceptable error of 33% = .% = .0303

n n = = = = 833833 observationsobservations((22))22 (.(.2525)(.)(.7575))

(.(.0303))22




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Islamic University of Gaza - PalestineWork Sampling Example

No. of Observations Activity

485 On the phone or meeting with a welfare client

126 Idle

62 Personal time

23 Discussions with supervisor

137 Filing, meeting, and computer data entry

833

All but inactive and personal time are work related. Percentage idle time = (126 + 62)/833 = 22.6%. Since this is less than the target value of 25%, the workload needs to be adjusted.


“TO LIVE, IS TO RISK DYING”




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