To trust your experimental results, you need to verify that your measurement system is accurate. You should verify the measurement systems that are used both to measure the response and to set the factor levels.
If the experiments are part of a larger improvement project, such as a six sigma project, the measurement system for the response should have been validated previously. Make sure that you verify the measurement system for the factors as well. For example, if you set an oven at 350° F, you need to be certain that the temperature is actually 350° F.