A local manufacturing company is interested in determining whether their employees are as happy with their jobs as other employees. The manufacturing company asked the workers, who volunteered to participate, to rate their happiness at work on a scale from 1 to 10 where 1 was not at all happy and 10 was extremely happy. The manufacturing company found that the mean happiness rating for their employees is 7.3. In the general population of workers in the United States, the mean happiness rating is 6.

What are the dependent and independent variables and their levels or measurement?