A paper company produces cardboard tubes for holding spools of paper. In order to test the strength of the tubes, each shipment is separated into three roughly equal parts based on time of production (early shift, middle shift, late shift); these strata typically correspond to a truckload of tubes. Five tubes from each subshift are randomly selected and then 3 rings are sawn from the end of each tube and tested for strength. The sample mean and standard error of the 45 rings are then computed.
Record your answers to the following questions. Discuss the answers with your group and submit your work.
Is this an experimental or classification study? Was selection of tubes randomized properly? Was selection of rings properly randomized? Suggest alternatives if you're unhappy with any aspects of the design. How should the mean and standard error be estimated?