Question 4 of 4 Smartphones: A study found that of 5300 cell phone owners in 2011, 612 owned a smartphone. The study was repeated in 2013, and 1200 out of 5300 cell phone owners owned smartphones. Part 1 of 2 (a) Construct an 80% confidence interval for the increase in the proportion of cell phone owners with smartphones between 2011 and 2013. Use the TI-84 Plus calculator and round the answers to three decimal places. An 80% confidence interval for the increase in the proportion of cell phone owners with smartphones between 2011 and 2013 is