13 Human Resource, Job Design, Work Measurement

Summary

The lecture explains how operations managers can allocate employees to jobs, sequence work to improve delivery performance, and calculate realistic labor standards. The central goal is to match work to employee skills while meeting customer deadlines and reducing delays, overtime, idle time, and work-in-process inventory.

Workforce Scheduling and Assignment

• Assignment method (Hungarian method): Use a time or cost matrix to assign each worker to one job while minimizing total completion time.
  • The manual procedure reduces rows and columns, covers the zeroes with the minimum number of lines, and adjusts the matrix until a complete assignment can be made.
  • If the number of workers and jobs differs, add dummy rows or columns to balance the matrix.
• Excel Solver alternative: Minimize total time calculated with SUMPRODUCT, subject to each worker and each job being assigned exactly once. Decision cells should be nonnegative; the lecture demonstrates the Simplex LP option.
• Example: The optimal assignment is Brian to job 2, Kari to job 1, Noah to job 4, and Chris to job 3, for a total of 21 hours. The manual and Solver methods produce the same result.
• Practical principle: Assign people according to their specific strengths. For example, pattern-making, sewing, and embroidery in garment production may each require different skills.

Job Sequencing Methods

Sequencing determines which job should be processed first. The appropriate rule depends on the service or production context and the performance goal.

• First Come, First Served (FCFS): Process jobs in arrival order. This is common in services such as banks and salons, though appointments or priority customers can change the order.
• Earliest Due Date (EDD): Process the job with the nearest deadline first.
• Shortest Processing Time (SPT): Process the shortest job first; this often improves average completion time.
• Longest Processing Time (LPT): Process the longest job first.
• Slack time: Prioritize the job with the least slack.

Slack = due date − current date − processing time

• Critical ratio (CR): A ratio above 1 means the job is ahead of schedule; below 1 means it is behind; equal to 1 means it is on schedule.

CR = (due date − current date) ÷ remaining processing time

• Johnson’s rule: For jobs that pass through two serial processes, repeatedly select the smallest processing time. Place it in the earliest open position if it belongs to process 1, or the latest open position if it belongs to process 2.

Five-Job Example

Rule Average completion time Average tardiness FCFS 18.6 days 9.6 days EDD 15 days 5.6 days Slack 16.4 days 6.8 days SPT 14.6 days Approximately 5.6 days

EDD improves on FCFS for both reported measures in this example, while SPT has the shortest average completion time. The lecture emphasizes choosing a rule based on the business priority—for example, minimizing lateness to protect customer commitments versus shortening internal completion time.

Two-Process Example

Johnson’s rule gives the sequence E–A–D–B–C, with a reported total completion time of 41 days and 10 days of total idle time across the processes.

Work Measurement and Labor Standards

Work measurement estimates how long a job should take under defined conditions, supporting staffing and capacity decisions.

• Normal time:

Normal time = observed time per unit × performance rating

- A worker operating 10% faster than normal has a rating of **1.10**; 10% slower corresponds to **0.90**.
- With multiple observations, calculate the average cycle time, excluding clearly abnormal observations when justified.

• Standard time:

Standard time = normal time ÷ (1 − allowance factor)

The allowance accounts for necessary rest, fatigue, and personal needs.

Examples

• Producing 20 units in an 8-hour day, with a 10% faster-than-normal rating and a 25% allowance:
  • Normal time: (480 ÷ 20) × 1.10 = 26.4 minutes per unit
  • Standard time: 26.4 ÷ (1 − 0.25) = 35.2 minutes per unit
• Multi-element observation: One 21-minute observation is treated as abnormal, and the remaining observations are averaged. The instructor reports a total normal time of 15.36 minutes and a standard time of 18.07 minutes, using a 15% allowance.

Scheduling Objectives and Actionable Takeaways

Scheduling should aim to:

• Meet agreed customer deadlines and reduce delays and response time.
• Minimize total time from order to delivery, overtime, idle time, and work-in-process inventory.
• Make effective use of available employees, machines, and facilities.
• Choose sequencing rules according to the desired metric. Compare completion time and tardiness rather than assuming one rule is best in every situation.
• Use manual assignment calculations for small problems and Solver or linear programming for larger ones.

Presenter and Sources

• Presenter: Hesti Maharesi
• Sources and tools mentioned: Excel Solver; Heizer and Render’s operations management textbook for allowance-factor tables; lecture slides and exercises.