|MadSci Network: Physics|
Probably the easiest and cheapest method would be to purchase a digital thermometer, which will generally read out to the tenth of a degree. You should be able to find one at any pharmacy for about twelve bucks.
I would be wary of any study which required a more precise body temperature measurement than one-tenth of a degree. Such a degree of precision in something as inconstant as body temperature will have little meaning.
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