Correct Answer - Option 2 : 6.22 minutes
Concept:
When time study is performed then
Observed Time (OT): It is the time observed by an observer
Normal Time (NT): It is the time required to complete a job by a normal average worker under normal working condition.
NT = OT × Rating Factor
Standard Time: It is the required to complete a job by taking all the uncertainty related to the production system into account
Allowances: It is the extra time provided to the worker above the NT to work continuously for long duration.
ST = NT + Allowances
Allowance are always given with respect to normal time.
Allowance = % of Normal Time
Calculation:
Given:
Given that cycle time 7.0, 6.0, 7.0, 8.0 minutes
\(Average\;OT = \frac{{7\; + \;6\; + \;7\; + \;8}}{4} = 7\;minutes\)
Rating Factor = 0.8
NT = OT × RF = 7 × 0.8 = 5.6 minutes
Allowance Fraction = 0.1
Allowance = 5.6 × 0.1 = 0.56 minutes
ST = NT + Allowance = 5.6 + 0.56 = 6.16 minutes ≃ 6.22 minutes