A factory recently experienced a chemical spill, and safety officers recorded the response behavior of on-site employees based on their department (Engineering, Maintenance, Security, or Cleaning). The table below summarizes whether the employees evacuated immediately or had a delayed evacuation. Assume this is a random sample from a much larger population. We want to use a significance level to test the claim that the evacuation response is independent of the employee’s department. How many degrees of freedom should be used for this test?
