Question

In work design measurement study, explain in your own words, the following terms:

• Observed time (OT)
• Normal time     (NT)
• Standard time  (ST)   

An industrial engineer working for you is given an assignment to determine the standard time (ST) for welding 2 metal parts together as a job function.

Your industrial engineer took 5 independent observations of the same welding job function and recorded the corresponding time it took to complete the job function. He complied the following table of data:

Observation                             Welding time (in minutes)

1. 2.50
2. 2.40
3. 2.45
4. 2.51
5. 2.49

If your industrial engineer has assigned a performance rating (PR) of 2.47 to the welding job function together with 15% as an allowance of of job time.

Calculate the respective:

• OT
• NT
• ST

Answer 1

Observed time = this is the time that is recorded after observing the work process in a time study. The formula for observed time is OT = average of recorded time

Normal time = this is the time that usually is required to perform a job in the process that is observed. The formula for normal time is NT = OT * rating factor

Standard time = this is the time that is assigned by the system to complete the work under normal circumstances considering all the allowances. Allowance could be break, setup time, maintenance time, etc. The formula for standard time is ST = NT / (1 – allowance factor)

In the given example problem,

OT = (2.5 +2.4 + 2.45 + 2.51 + 2.49)/5 = 2.47

The observed time is 2.47 minutes

The performance rating is 2.47. This means the performance observed is at 247% of the normal time. This translates into

NT = 2.47*2.47 = 6.1 minutes

This means usually they perform the work in 6.1 minute but since they were performing at 247% efficiency, they got it done in 2.47 minutes.

The standard time is

ST = 6.1/(1-0.15) = 7.17 minutes

The company usually allocates 7.17 minutes for the workers to finish their work.