A teacher observes that if Lisa and Ian work independently
on the same problem, Lisa has a 90% chance of solving the
problem and lan has a 70% chance of solving it. What is
the probability that at least one of them solves the problem?
A 0.97
B 0.63
C 0.2
D 1

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