The article "Measuring and Understanding the Aging of Kraft Insulating Paper in Power Transformers" (IEEE Electrical Insul. Mag., 1996: 28-34) contained the following observations on degree of polymerization for paper specimens for which viscosity times concentration fell in certain middle range. 415 434 454 421 437 463 421 439 465 422 446 425 447 427 448 431 453 Standards call for a true mean degree of polymerization of 440. Historically, the degree of polymerization has had a population standard deviation (sigma) of 15.5

[(a)] Construct and Interpret a 95% confidence interval for the true mean degree of polymerization.