An administrator in a very large company wants to estimate the mean level of nitrogen oxides (nox) emitted in the exhaust of a particular car model in their very large fleet of cars. historically, nitrogen oxide levels have been known to be normally distributed with a standard deviation of 0.15 g/ml. what is the parameter of interest that the administrator wants to estimate?

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.

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