SPC Charts prevent bad baking

Used as quality tools, Statistical Process Control (SPC) charts allow you to measure a process’s stability.  It also gives you specific thresholds that show when you process is producing results that are unacceptable, the control and specification limits.  Pretty heady stuff?  Try this real-world example out …

An appliance repairman left my house not more than ten minutes ago, after 20 minutes of work, $75 richer.  My wife had pointed out that the oven was not heating consistently (our specification limits — hey, I like to cook), varying in temperature as much as 30 degrees from what we set on the control panel.

The repairman pointed out that our cheap oven thermometer (he didn’t actually call it cheap, he was much too polite for that, but the thermometer was inexpensive and not constructed very well …

(exciting game-show music)

POP QUIZ — can anyone out there tell describe this quality concept?  Materials inadequate to deliver consistent results over time are …?  Who is attributed with this quality concept?

Drop me an email … GYoung.PMP@Gmail.com with your answers.  All those with the two correct answers will be entered into a drawing to take place on 3/15 for …

(tell ’em what they’ll win, Nanny John)

A  b r an d  n e w,  shrink-wrapped PMBOK®!   (crowd ooohs.  Applause)

Yes, that’s right.  Get your very own Project Management Body of Knowledge, complete with protective cellophane sheath.  Impress your friends, your coworkers and relatives with your instant access to the good practices of project management known the world ’round.

Get those emails in.  Drawing is 3/15/11!


OK, we are back after that gratuitous pop-quiz interruption.  Back to the repair visit.  The repairman mentions that his spec sheet from the manufacturer “on this particular appliance” permit operating temperatures within 50 degrees of the temperature set on the control panel.  So, in our case, if we had set the oven at 400 degrees, the manufacturer would say there was a problem only if the actual temperature reading within the oven (ignore the reading from our inaccurate oven thermometer — we are getting a new one since it was not producing valid results … more on validation and verification in just a second), taken with a calibrated instrument was 375 degrees and below or 425 degrees and above.

So what’s the lesson?

1) The target heat (set by the control panel) can be verified by taking readings from an instrument that produces measurements known to be consistent with a standard (they are valid).  The manufacturer establishes a range of acceptable appliance performance (known as Control Limits on the PMP® exam) and if a measure falls outside of those control limits, they will take action to correct the situation.

2.) Our cookies do not bake well with such wide variations in heat (our Specification Limit is … “the heat set should be the heat get”) not as tolerant as the manufacturer’s, which is a recipe for unhappiness.

So, in life, as on the PMP® exam, you may run into situations in which a process is within statistical control but cookies get burned in the process.

You are great!


About Gordon Young

Need 10's of millions? Start here. Keynote speaker, coach and instructor. I help companies tap into the creativity and energy of their teams resulting in profit, engagement and well-being.
This entry was posted in Quality. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s