3, No. 11
from Dr. Cleary
are four types of data:
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.
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,
data. Interval data reflects a measurement of the difference between
$2,400 and $2,200 = difference $200
6 feet and 5 feet = one foot difference
10 days and 2 days = eight days difference
data. Distinguishes among items using a common denominator, that is,
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
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 email@example.com
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