Question

Arsenic is an element that occurs naturally in groundwater, but a mean greater than 8.0 parts per billion indicates that the groundwater has been contaminated. Local officials are concerned about a well in an area of the city near a factory. On 50 consecutive days, water was randomly sampled from the well. Assume the water in the well has a mean arsenic level greater than 8.0 ppb. Based on the data, if we find moderate/strong evidence against the null hypothesis and conclude the mean arsenic level of the water is greater than 8.0 ppb, we have made ____________.

Answer 1

decision

Explanation:

Based on the data, if we find moderate/strong evidence against the null hypothesis and conclude the mean arsenic level of the water is greater than 8.0 ppb, we have made decision

Answer 2

Based on the data, if we find moderate/strong evidence against the null hypothesis and conclude the mean arsenic level of the water is greater than 8.0 ppb, we have made ____________.

a correct decision.

Explanation:

Since there is enough evidence to conclude that the mean level of arsenic is greater than 8.0 ppb, the correct decision has been made. There is no type I or type II error. The type I error (called a false positive) occurs if we reject the null hypothesis when it is true. Since we have simply rejected the null hypothesis when the alternate hypothesis is true, and the null hypothesis should be rejected, a correct decision has been made.