Cadmium, a heavy metal, is toxic to animals. Mushrooms, however, are able to absorb and accumulate cadmium at high concentrations. A government set a safety limit for cadmium in dry vegetables at 0.5 parts per million (ppm). The cadmium levels in a random sample of one species of edible mushroom are in the accompanying data set. At the 5% significance level, do the data provide sufficient evidence to conclude that the mean cadmium level in this species of mushroom is greater than the government’s recommended limit of 0.5 ppm? Assume that the population standard deviation of cadmium levels in this species of mushroom is 0.44 ppm. Preliminary data analyses indicate that applying the z-test is reasonable. (Note: The sum of the data is 7.89 ppm.)

a. State the hypotheses for the onemean z-test.

b. Determine the critical value(s).