Page 42 - Six Sigma Demystified

Chapter 1 d e p loy m e n t s t r at e g y 23

versely, those at the operations or process levels in the organization can drill up
to understand how their metrics relate to stakeholder value.
For example, the little y’s for the customer- satisfaction score (Y ) in a restau-
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rant chain might be

Customer satisfaction = function of (service quality, culinary satisfaction,
restaurant availability, price, . . . )

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These business- evel little y’s will become the operations- evel big Y’s.
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Operations- level big Y’s are useful for Six Sigma project selection criteria be-
cause they are the operational parameters that are perfectly aligned with the
business- level metrics.
The operations- level little y’s for service quality of the restaurant chain may
be written as

Service quality = function of (wait time, friendliness of staff, cleanliness of
facility, order accuracy, . . . )
Each of the operations- level little y’s may be broken down further into their
components in the process- level matrix. For example,

Wait time = function of (cycle time for cooking, number of staffed
registers, time of day, . . . )

This resulting function then can be used to

• Establish conditions necessary for process optimization and/or variation
reduction
• Provide process- level Six Sigma project metrics

• Define critical metrics for ongoing process control
These transfer or flow- down functions, which relate the big Y’s to their cor-
responding little y’s, are determined through regression and correlation analy-
ses. Data are collected through designed experiments, data mining, surveys,
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focus groups, and critical- ncident techniques. The functions allow process- evel
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metrics to be linked to both customer requirements and business strategy.
An example for a software company is shown in Figure 1.6. For each of the
key stakeholder groups (i.e., customers, shareholders, and employees), metrics
were established at the business level (ovals), operations level (diamonds), and
process level (rectangles). At the business level, for example, the retention rate
for customers is tracked on a monthly basis as a general indicator of overall