"Supposed that an internal report submitted to the managers at a bank in Boston showed that with 95 percent confidence, the proportion of the bank's customers who also have accounts at one or more other banks is between .45 and .51. Given this information, what sample size was used to arrive at this estimate?"
We're solving for 'n' . I have a CI of 95% which is z=1.96. I'm thinking the pbar is 0.48 (the average between 0.45 and 0.51) but I'm still unsure how to solve for 'n'.