November 2001 Vol. 3, No. 11
Quality Quiz from Dr. Cleary

Congratulations!
You're right!

 There are four types of data: 1. Nominal. The word 'nominal ' comes from a Latin word, meaning 'name. ' Nominal data allows for distinctions to be made between items, such as male or female; programmer or nonprogrammer; rainy or not rainy. 2. Ordinal data. The word ordinal comes from another Latin word, meaning 'order. ' Ordinal data identifies distinctions among items with respect to degree or order: e.g., small, medium, large; short, tall; or big, little. 3. Interval data. Interval data reflects a measurement of the difference between items. \$2,400 and \$2,200 = difference \$200 6 feet and 5 feet = one foot difference 10 days and 2 days = eight days difference 4. Ratio data. Distinguishes among items using a common denominator, that is, percentage. My day class is 50 percent female. My evening class is 30 percent female. 30 percent of part A are bad 20 percent of part B are bad Raney has ratio (commonly known in SPC as attribute) data, rather than interval data. A p-chart or an np-chart would be appropriate to use in this case. Note: Under some circumstances, some would suggest that an X-MR chart is the right choice here. For more discussion, contact me at mike@pqsystems.com