Attribute vs. variable data

[Cynthia Nadalini <invenia@guate.net>]

A question for the staticians:
In a production line, they measure the efficiency by first counting how 
many bags of product were produced in a day, how many bags they should have 
produced according to the machine specifications, and then divide the real 
into the ideal amount of bags produced and multiply it by 100 to get a 
percentage.  They are using an np control chart to plot that efficiency, 
but I was wondering if that efficiency satisfied the assumptions of the 
binomial model, or if an X chart should be made instead.  Why or why not? 
 Thanks a lot.

Cynthia N.
INVENIA
Guatemala, Central America
invenia@guate.net
Phone/Fax: (502) 5946161
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