Getting Time Standard: Stopwatch Time Study

It is vital to every business to set expectations for its employees, balance workload, manage constraints, determine staffing levels and crew size, schedule and eliminate waste and non-value-added activity. Thus, work measurement is the technique to set off, for any organization where human and machines contribute to output, to customer service, or even to cost.

Work measurement provides tools to manage the business better. Work measurement engages the estimation of the amount of human effort needed for producing a unit of specified output from an operation. The amount of time that is usually taken by in a well trained worker, operating under normal working conditions, to produce one unit of output is referred as work standard.

A work standard is used when assigning work to employees, scheduling work in departments, and evaluating employee performance. Organizations use several different techniques to set work standards. These are stopwatch time study, work sampling, and predetermined motion times.

Stopwatch Time Study

Time study is a procedure used to measure the time required by a qualified operator working at the normal performance level to perform a given task in accordance with a specified method. It usually includes methods study. The time study analyst has to observe the methods while making a time study. It is advantageous, while the time study is being conducted, the analyst should also look for opportunities for methods improvement.

The procedure for time study can best be described with the following steps:

Step 1: Define objective of the study. This involves statement of the use of the result, the precision desired, and the required level of confidence in the estimated time standards.

The desired accuracy is often stated as a percentage of the average of the observed time. The sample size needed to achieve a certain level of accuracy can be computed using the formula:

Sample size:

n = (zs/ax)²

n = (zs/e)²

where: n = number of observations needed

x = mean of the observed time

a = allowable error as percentage of average time

e = maximum acceptable error

s = standard deviation of observed time

z = number of normal standard deviation needed for desired confidence

Typical values of z, cumulative probabilities of the Standard Normal Distribution used in this computation are:

Confidence Level          z value

          90%                     1.65

          95%                     1.96

          95.5%                  2.00

          98%                     2.33

          99%                     2.58

Example:

A time study analyst wished to estimate the time required to perform a certain job. A preliminary work showed a mean of 6 minutes and a standard deviation of 2 minutes. The desired confidence is 95%. What`s the sample size needed if the desired error is (a) + 10% and (b) one-half minute of the sample mean?

for (a)

n = [1.96(2)/0.10(6)]²

n = 42.68 or 43 sample size

for (b)

n =[ 1.96(2)/0.5]²

n = 61.47 or 62 sample size

Step 2: Analyze the operation to determine whether standard method and conditions exist and whether the operator is properly trained. If need is felt for method study or further training of operator, the same may be completed before starting the time study.

Step 3: Select Operator to be studied if there is more than one operator doing the same task.

Step 4: Record information about the standard method, operation, operator, product, equipment, quality and conditions.

Step 5: Divide the operation into reasonably small elements.

Step 6: Time the operator for each of the elements. Record the data for a few numbers of cycles. Use the data to estimate the total numbers of observations to be taken.

Step 7: Collect and record the data of required number of cycles by timing and rating the operator. Performance rating is invariably required when setting standards by stopwatch time study due to some cases: the operator being observed may work faster than average (naturally quicker, showing off, or speeding up due to nervousness from being studied); and the operator being observed may work more slowly than the average (just naturally slower, slowing down on purpose to confuse the time study analyst, or excessive interruptions, and so on). The standard performance rating is denoted as 100 percent.

Step 8: For each element calculate the representative watch time or observed time. Multiply it by the rating factory to get normal time.

Normal time =Observed time) x Rating factor

Example: An operator takes an average of 10 minutes to complete a particular task. Operator’s performance rating (pace) is 110%. What is the normal time for completing this task?

NT = 10 minutes (110%/100%)

NT = 11 minutes

Add the normal time of various elements to obtain the normal time for the whole operation.

Step 9: Determine allowances for various delays from the company's policy book or by conducting an independent study. The readings of any time study are taken over a relatively short period of time. The normal time arrived at, therefore does not include unavoidable delay and other lawful lost time, for example, in waiting for materials, tools or equipment; planned inspection of parts; interruptions due to valid personal need, etc. It is necessary and important that the time study analyst applies some adjustment, or an allowance to pay off for such losses, so that time standard is established for the given job.

Step 10: Determine standard time by adding allowances to the normal time of operation.

Standard Time = (NT) x (1 + allowance factor)

Using Allowance Factor for task:

AF_task: ST = (NT)(1 + AF)

Allowance Factor for shift or total work period:

AF_shift: ST = NT/ (1 – AF)

AF_task is most often used in practice which assumes that allowances are added to normal time. If presumes that allowances should be applied to the total work period, then AF_shift should be used.

Example: An operator takes an average of 10 minutes to complete a particular task. Operator’s performance rating (pace) is 110% and there is an allowance of 15%. What is the normal time and standard time for completing this task?

Given the NT = 11 minutes,

Using AF_task, therefore, the standard time is,

ST = 11 x (1 + 0.15) = 12.65 minutes

Today, Work Measurement studies and establishing time standards is very easy with the use of a unique TimeCorder device. Let's watch this video.

Guide Question:

When can we say that time values or the computed time standard is actually the standard? (Write your answer in the comment section below)

Let's try this quiz!!!

About the author

Suzette Masangcay-Mercado is currently taking up Master of Science in Engineering Education major in Industrial Engineering at Rizal Technological University, Mandaluyong City. She is a faculty member of Batangas State University, Alangilan Campus under the College of Engineering, Architecture and Fine Arts.