A government agency is going to keep records of nitrogen levels in a lake that is mostly surrounded by farmland. High nitrogen levels may indicate incorrect or excessive use of fertilizers. Water samples will be taken at 5 meters depth from 28 locations on the lake and nitrogen concentration will be measured in milligrams per liter of water. There was debate over whether the locations to be sampled should be spread randomly over the lake's surface, or positioned at the mouths of watercourses that feed into the lake (e.g., rivers, creeks, gullies).

(a) Briefly describe a method by which 28 locations could be selected randomly on the surface of a lake. [Note: when referring to random selection you must describe how you would achieve randomness.]

(b) As indicated above, two sampling methods are being considered. Which of these should be preferred if the government agency is specifically concerned with -

(i) regulating fertilizer use on farms

(ii) environmental management, including water quality