A consultant wants to ask workers at a factory about the workers' job satisfaction. Which of the following best describes a cluster sample of workers? a. The consultant takes a list of the workers and selects every 6" worker until 60 workers are selected.
b. The consultant forms 5 groups of workers based on the workers' shifts. Then, he selects 12 workers at random from each group.
c. The consultant forms groups of 12 workers based on the lengths of time the workers have worked at the factory. Then, he randomly chooses 5 groups and selects all of the workers in these groups