A sample of a radioactive isotope had an initial mass of 370 mg in the year 2007 and decays exponentially over time. A measurement in the year 2012 found that the
sample's mass had decayed to 80 mg. What would be the expected mass of the
sample in the year 2020, to the nearest whole number?

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables