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 .