Correlation is how one variable changes as the other variable changes. A correlation is a relationship between two things such as smoking and lung cancer. (Tanner, 2012) In manufacturing there are relationships between many things. For example in manufacturing employee wage is based not just on knowledge but also on performance and there is a direct correlation between the wage paid and performance. There are some variables to this such, as a knowledgeable employee who does not put forth a good effort will not be paid as much as another with the same experience or less who works harder and is more productive. To test this you would need to track employees productivity and compare it to their wages. The null hypothesis is that an employee who is knowledgeable and works harder is paid more. The alternate hypothesis is that all employees are paid the same regardless.