A sample survey is designed to estimate the proportion of sports utility vehicles being driven in the state of California. A random sample of 500 registrations are selected from a Department of Motor Vehicles database, and 21 are classified as sports utility vehicles. (a) Use a confidence interval to estimate the proportion of sports utility vehicles in California. (Round your answers to three decimal places.) (b) How can you estimate the proportion of sports utility vehicles in California with a higher degree of accuracy? (HINT: There are two answers. Select all that apply.) D increase z 2 by increasing the confidence coefficient D increase z 2 by decreasing the confidence coefficient Cl decrease the sample size n Cl increase the sample size n Cl decrease z 2 by decreasing the confidence coefficient D conduct a non-random sample Cl decrease z 2 by increasing the confidence coefficient