In Exercises 9-20, identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster.

1. Cormorant Density Cormorant bird population densities were studied by using the "line transect method" with aircraft observers flying along the shoreline of Lake Huron and collecting sample data at intervals of every 20 km (based on data from Journal of Great Lakes Research) 
2. Reported and Observed Results A Harris Interactive study involved 1013 adults who were interviewed about washing their hands in restrooms and another 6336 adults who were observed in public restrooms.
3. Criminology Researchers randomly selected 50 convicted felons from each category of burglary, auto theft, and assault.
4. Exit Polls During the last presidential election, CNN conducted an exit poll in which specific polling stations were randomly selected and all voters were surveyed as they left the premises.