A pesticide formulation machine is set to maintain 180 ml of active ingredient in a liter (1000 ml). (18% AI). Seventeen 1 liter bottles of pesticide are selected at random and their active ingredient contents are determined. The percentage of active ingredient in the bottles are as follows:

17, 19, 21, 16, 18, 20, 20, 19, 16, 15, 20, 19, 18, 17, 18, 20, 17.

Is there a reason to believe that pesticide formulation machine is defective? Use = 0.05 and in your answer, clearly state a null hypothesis and conclusions.