18.20 Immigration. Suppose that 29% of all adult Americans think that the level of immigration to the United States should be decreased. An opinion poll interviews 1520 randomly chosen Americans and records the sample proportion who feel that the level of immigration to this country should be decreased. This statistic will vary from sample to sample if the poll is repeated. The sampling distribution is approximately Normal with mean 0.29 and standard deviation about 0.012. Sketch this Normal curve and use it to answer the following questions. a. The mean of the population is 0.29. In what range will the middle 95% of all sample results fall? b. What is the probability that the poll gets a sample in which fewer than 27.8% say the level of immigration to this country should be decreased?