Question

A biologist is studying the levels of arsenic that are naturally produced in some ground water sources. A mean level of 8.0 parts per billion (ppb) and less is considered safe for agricultural use. A random sample of 60 tests of the ground water at different locations in the town of Howick yields a sample mean of 8.46 ppb with a standard deviation of 1.3 ppb. Is there enough evidence to conclude that the arsenic levels are too dangerous to use for agricultural purposes at the 98% confidence level? Conduct a complete hypothesis test.