As Lean Six Sigma practitioners we often hear words like “better, faster, cheaper” without anyone really understanding what that looks like. One of our duties is to convert abstract “voice of the customer” (VOC) requirements into a measurable output variable.
A CTQ tree is a six sigma tool used to transform VOC (cold) into something measurable (temperature). The same can be accomplished with words like affordable, colorful, clean, long and so on. So what temperature is “Cold” for beer? Answer: about 47 degrees (range for Ale beer is 44-52 degrees). So with random samples and a simple thermostat we can determine the amount of output variation and if our process is producing defects.
The process: after brewing is complete the beer is stored at desired temperature in an insulated storage vat. At some future point (no more than two weeks at Ellis Island Brewery) beer is transferred to casino bar via pipes that run across the roof (a very hot roof). The beer must remain at 47 degrees during the transfer process, a pipe coolant system is used for this purpose. Bartender then pours beer into cold glass and hands it to me (yes, I went to the Gemba multiple times during my research).
|Customer Need||Drivers||CTQ Characteristics|
|Cold Beer||Storage Vat insulation||Beer stored at 47 degrees|
|Transfer pipe coolant system||Beer transferred from storage to tap at 47 degrees|
|Bar refrigerator/freezer||Beer mug at 38 degrees|
By knowing the drivers that produce the VOC requirements helps us understand the systems that add value, shows us what we actually have control over (coolant systems and insulation), identify potential failures of those systems, and gives us a good starting point if we need to accomplish a root cause analysis. Bottom line: it’s very useful.
So the next time you hear abstract VOC requirements, think of cold beer and CTQ trees, I know I will. Hope you have a “great” day.