Questions 18-19: According to the U.S. Census, the mean household income in the United States is $57,617 with a standard deviation of $104,393. These estimates were based on a sample of 2,229,872 households. 18. Construct a 95% Confidence Interval. A. ($57425, $57779) B. ($56480, $58754) C. ($56380, $58854) D. ($57480, $57754) Page |4 Name Class Date 19. The large standard deviation seems to suggest a high level of variability among household incomes in the U.S. Why then is the confidence interval so narrow? A. The large value of the sample mean. B. Confidence intervals are always narrow when estimating a mean. C. The large sample size. D. The large population size