Issues with Data Collection – the Flint MI Water Crisis

The city of Flint, Michigan changed its water source from the Detroit water system to the Flint River in April, 2014 in order to save money.  Residents soon began to complain about the water’s color, taste and odor, and to report rashes and concerns about bacteria.  The Flint city government proclaimed at that time that […] read more

On July 30th, 2016, posted in: Six Sigma by Tags: ,

Lies and Statistics……

One of my Black Belt students recently submitted his final project report.  He used the two proportions test in Minitab to compare the proportion of on time performance for completion of employee appraisals, before and after improvement.  I sent him the following feedback regarding this test. “Hi.  Your null and alternate hypotheses are correctly stated.  […] read more

On July 9th, 2016, posted in: Articles, Six Sigma by Tags: ,

The Central Limit Theorem

Although the central limit theorem can seem abstract and devoid of any practical application, this theorem is actually quite important to the practice of statistics.  As we will see, this theorem allows us to make some assumptions about a population. In order to understand the basis for the Central Limit Theorem, consider a population of […] read more

On June 16th, 2016, posted in: Articles, Six Sigma by Tags: ,

Percentage data – is it continuous or discrete?

I received the following email in response to a previous article about discrete and continuous data.  The exchange has been edited slightly for ease of reading. “Hello Roger.  I enjoyed your posted article regarding discrete and continuous data. I have encountered similar discussions with other Industrial Engineers and Master Black Belts over the years. As […] read more

On June 2nd, 2016, posted in: Six Sigma by Tags: , ,