Question of the Week

Q: What’s the difference between variable data and attribute data?
A: Variable data are “measurement information” and subject to change. Attribute data, meanwhile, are data that show that an item or feature either exists or doesn’t exist, so-called “pass/fail” or "go/no-go" information.
(from The Quality Improvement Glossary, ASQ Quality Press, 2004.) 

These articles from the ASQ archives offer in-depth discussion of the two data types:

Which Control Chart Should You Use?
by Larry Weinstein and Robert J. Vokura
Six Sigma Forum Magazine, May 2006
Thoughts on evaluating control charts to make sure they truly help you evaluate performance and improvement in a Six Sigma project. Logged-in members/subscribers: Instant Access. Or you can buy a PDF.

Effectiveness of a Product Quality Classifier
By E. Bashkansky, S. Dror, R. Ravid, and P. Grabov
Quality Engineering, July 2007
Evaluating the effectiveness of a quality sorting station, taking into account the availability of prior information. Logged-in members/subscribers: Instant Access. Or you can buy a PDF.

Factorial Effects, Random Blocks, and Longitudinal Data: Two Simple Analysis Methods
By J. Engel
Journal of Quality Technology, January 2008
This article proposes two methods for modeling factorial effects in random-block experiments with longitudinal

response. Model estimation and model testing with both methods are discussed. Logged-in members/subscribers: Instant Access. Or you can buy a PDF.