Measuring Service Time

It’s hard to measure what you can’t see and what you can’t manage you can’t measure.  This makes measuring and managing the flow of work through a process difficult since flow is a concept of time.  Time is hard to see.  Many organizations are comfortable with taking snapshot measurements that freeze time.  But measuring process flow over time can be both hard to conceptualize and hard to do.

The overlap and inconsistencies in use of the common measures of flow and time is an indicator of the complexity.  To establish a framework for discussion consider the following definitions of time as found in the Agile & Lean Glossary:

Wall Clock Time – The continuous measure of time between two milestone events

Cycle Time – The wall clock time necessary to complete a single item of work

Lead Time – The wall clock time from when a customer request is made until the request is fulfilled

Service Time – The wall clock time necessary to provide a service from start to finish

Cycle time and lead time are probably the most commonly used terms to measure process flow.  However both measures are just as commonly misused.  Cycle time is the wall clock time to complete one cycle or unit of work such as fill out a form or send an email.  Lead time is the wall clock time to fulfill a customer request.  Both are used to describe the wall clock time to provide any service from start to finish but each usage is incorrect.

To measure the time both to fill out a form and send an email is actually the sum of the two individual cycle times, or the total cycle time.  It’s possible to measure the total cycle time of each step of a process.  But what should the sum of the total cycle times of each process step called.  The total total cycle time?  Can see where this is going?  What do you call the measure of time to perform two sequential processes?

Lead time has similar constraints.  It is strictly defined as the time from a customer request to fulfillment.  If a customer buys a computer on the Internet the lead time is from order submittal to the delivery of the computer to the customer’s location.  Good to know, but what if it is also helpful to know the time from order completion to the computer shipment to the customer?  By definition that is not called lead time.  Partial lead time?  Or perhaps total total total cycle time?

Time for a New Approach
Both cycle time and lead time are important measures but their definitions are very specific and do not apply to measuring flow for discrete segments of a process.  Service time is defined to fill the gap left by cycle and lead time. 

Service time measures the flow of work/information between any two points of a process.  It is called service time to emphasize that it is a measure of the wall clock time to provide a specific service either to either an internal or external customer. 

Examples of service time (measured in wall clock time):

• The time to capture a customer request at a walk-in customer service counter
• The time to finalize a customer request and submit it to engineering
• The time to complete the engineering design of a customer request
• The time to obtain customer approval of a completed engineering design

Time for Service
Service time could be established for a combination of the above process segments.  As well each of the above segments could be broken into more granular service time measurements.  In each of the above examples, a service level agreement (SLA) based on service time could be established as a measureable objective for those providing the service.

Lead time and cycle time were originally developed as measures of manufacturing processes.  In a non-manufacturing environment their use is limited due to their specific definitions.  Or worse their definitions are extended to serve other measurement functions leading to miscommunication and confusion.  Service time avoids these limitations by specifying both the service and the time to provide that service, providing an important measure for effectively managing that service.

The next post, Measuring Process Flow, describes how to use service time as a measure of process flow.