... and it really has sped up transaction time averaging less than nine seconds. A typical transaction can take up to sixteen seconds to charge without obtaining a signature per David Bonalle, at American Express. In the Phoenix trial, with 268 merchants, ExpressPay prompted customers to use their American Express accounts 33% more often." (http://www.cardtechnology.com/cgi/bin/readstory.pl?story=20040102CTMC230.xml) Causes of Variation There are two general causes of variation - chance and assignable. "Chance variation is variation that is random in nature. This type of variation cannot be completely eliminated unless there is a major change in the equipment or material used in the process. Assignable variation is variation that is not random. It can be eliminated or reduced by investigating the problem and finding the cause." (Lind, 2002, p.626) For the ExpressPay smart chip-carrying fob it is important to ensure that the smart chip be of the same quality and not varied. How can ...

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