Process Capability and Capacity

COB 300 C

Dr. Busing

Process Capability

• Processes are inherently variable.

• Engineering sets tolerances or specifications that tell range of values in which individual units must fall in order to be deemed “acceptable.”

• Statistical limits that reflect the extent to which sample statistics can vary due to randomness alone are called control limits.

Process Capability (cont’d)

• Process variability is natural or inherent (i.e., random) variation.

• Capability analysis is used to determine whether or not the inherent variability of the process output falls within the acceptable range of variability allowed by the design specifications for the process output. It refers to the ability of a process to meet the specifications set by the customer or designer.

Process Capability (cont’d)

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Process Capability (cont’d)

• Meaning -– Process capability of 1.00 or greater means that

the process will produce virtually 100 percent conforming output (the range of the process output permitted by specifications is larger than the actual range of the process).

– Process capability of less than 1.00 means that the process generates output over a larger range than the specification limits permit.

Process Capability (Example)

• Food served at a restaurant should be between 38o C and 49o C when it is delivered to the customer. The process used to keep the food at the correct temperature has a process standard deviation of 2 o C. What is the process capability of the process?

• If the mean temperature of the food prior to delivery is 43.5 o C, what proportion of all meals will be delivered at an acceptable temperature?

• If management wants to ensure that only 0.1% of meals are delivered either too warm or too cold, what specifications should they set for delivery temperature?

• What other course of action could management take to make sure that only 0.1% of meals are delivered either too warm or too cold?

Process Capability (Example)

Food served at a restaurant should be between 38o C and 49o C when it is delivered to the customer. The process used to keep the food at the correct temperature has a process standard deviation of 2 o C. What is the process capability of the process?

Process Capability (Example)

If the mean temperature of the food prior to delivery is 43.5 o C, what proportion of all meals will be delivered at an acceptable temperature?

Process Capability (Example)

If management wants to ensure that only 0.1% of meals are delivered either too warm or too cold, what specifications should they set for delivery temperature?

Process Capability (Example)

What else could management do?