Union members in a large firm work in three departments: assembly, maintenance, and shipping/receiving Twenty of a random sample of 30 assembly workers say they intend to ratify the new contract negotiated by union leaders and management. This compares to 30 of 40 maintenance workers and 25 of 50 shipping/ receiving workers who say they will ratify the contract.
At the 0.025 level of significance, test the null hypothesis that the population proportions are the same for all three departments.