Stats Made Easy

Practical Tools for Effective Experimentation

Thursday, April 27, 2006

Repeated measure versus true replication

It was my pleasure yesterday to teach design of experiments (DOE) at the Ohio State University's Fisher College of Business for their Web-Leveraged Six Sigma Black Belt program. It turned out that one of the participants, Dennis Dubose -- a statistician with Sumco USA, teaches DOE also, so we compared notes. He shared a nice explanation of the difference between simply repeating measures versus performing a true replication of the system setup for purposes of estimating error. Imagine you flip a coin and it comes up heads. You ask a colleague to look at it and call out the result. Then another colleague is asked to observe the coin and state which side came up. This is a repeated measure. A true replication is accomplished only by re-flipping the coin.


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