A sample is chosen randomly from a population that can be described by a Normal model. Complete parts a and b below. a) What?s the sampling distribution model for the sample mean? Describe shape, center, and spread. Choose the correct answer below. A. Normal, with a center at a and a standard deviation of mu/root n. B. Normal, with a center at sigma/ root n and a standard deviation of mu. C. Normal, with a center at mu/ root n and a standard deviation of sigma. D. Normal, with a center at mu and a standard deviation of sigma/ root n. b) If a larger sample is chosen, what?s the effect on this sampling distribution model? A. The standard deviation will be smaller, but the center will remain the same. B. The center will be smaller, but the standard deviation will remain the same. C. The standard deviation will be larger, but the center will remain the same. D. The center will be larger, but the standard deviation will remain the same.