Vol. 9, No. 3

March 2007

PQ Systems

Healthy control charts

Quality Quiz: With a video!

Six Sigma

Data in everyday life

Bytes and pieces

FYI: Current releases


Send Quality eLine
to a friend!

Just type in your friend's email below:


Sign up
If you received this newsletter from a friend and want your own subscription to Quality eLine, click below.

Subscribe to Quality eLine




Quality Quiz from Professor Cleary

"B" is correct.

Click here for a more complete video explanation

There are four types of data:

  • 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, day shift or night shift, etc.
  • 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., male, female; small, medium, large; short, tall; or big, little.
  • Interval data. Interval data reflects a measurement of the difference between items. The distance between 6 and 7 is the same as that between 1 and 2.

$2,400 and $2,200 = difference $200

6 feet and 5 feet = one foot difference

10 days and 2 days = eight days difference

  • Ratio data. Distinguishes among items using a common denominator, that is, percentage. Ratio data has a defined origin—zero.

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.

Click here to register to win a free Quality Gamebox program.


Copyright 2007 PQ Systems.
Please direct questions or problems regarding this web site to the Webmaster.