In both cases, it is often mathematical convenience rather than the accuracy of the models that motivates their use.
This is usually done for mathematical convenience.
Robertson has stated that the assumption of word independence is not justified and exists simply as a matter of mathematical convenience.
A better approach is to allow rate variation, and the gamma distribution is usually used because of its mathematical convenience.
Another quantity often used for mathematical convenience is the Fano factor:
This is a mathematical convenience and does not imply that there are actually monopoles in the magnet.
Were the parallel existences genuine, or were they just mathematical conveniences?
"A mathematical convenience, not a fact," said Claymore.
This showed for the first time that the magnetic vector potential, hitherto a mathematical convenience, could have real physical (quantum) effects.
The very concept was nothing more than a mathematical convenience applicable only to some localized areas for purposes of measurement.