Page 279 - Six Sigma Demystified

Part 3 s i x s i g m a to o l s 259

When to Use

Analyze Stage

• To prioritize process activities or product features that are prone to failure
Improve or Design Stage

• To determine high-risk process activities or product features in the pro-
posed improvement

Methodology

The following steps are required for the FMEA:

• Define the function of each process step (or product feature, for designs).
For example, in a sales process:
Process step: Enter the product ID number for each purchased item.
Function: Links to the product database to identify the item numbers
necessary for the products being purchased.
• Identify the failure mode and its effect for each function. In defining fail-
ure modes and their effects, it is helpful to ask, “What could go wrong?”
or “What could the customer dislike?” For example:
Function: Links to the product database to identify the item numbers
necessary for the products being purchased.
Failure mode 1: Product ID mistyped.
Effect of failure mode 1: Wrong product shipped.
Failure mode 2: Item numbers not correctly defined in database.

Effect of failure mode 2: Wrong product items shipped.
• Define the severity for each of the failure modes. Table T.10 provides a
good means of identifying the severity for a given failure effect. Granted,
defining a severity level is subjective. In the example that follows, a sever-
ity of 5 or 7 could have been reasonable choices; the “right” answer can
never be known, but consistency within a given analysis or between anal-
yses that compete for resources certainly is important for meaningful pri-
oritizations. For example:
Failure mode 1: Product ID mistyped; severity = 6. From Table T.10,
severity 6 is described as “Moderate disruption to operations. Some loss
of product or service may occur requiring moderate remedy. Customer
will complain; product return likely.”