To estimate the amount of stationary being "used" by employees of a national company, the researcher first randomly selected 10 branches (among 100's of branches) across Canada and every employee in those branches was asked to report the amount of stationary they have used in the past 12 months.

a) Identify the sampling method used above. Make sure you provide a detailed justification of your answer.

b) Does the above sample involve any sampling error? If so, briefly justify. If not, briefly explain why not.

c) Does the above sample involve any response bias? If so, briefly justify. If not, briefly explain why not.