The World Data Centre for Greenhouse Gases collects and archives data for greenhouse and related gases in the atmosphere. One such data set lists the level of carbon monoxide gas (measured in parts per billion) in the atmosphere each week at the Cold Bay, Alaska, weather station. The weekly data for the years 2000–2002 are saved in the COGAS file.

a. Identify the variable measured and the corresponding experimental unit.

b. If you are interested in describing only the weekly carbon monoxide values at Cold Bay station for the years 2000–2002, does the data represent a population or a sample? Explain.