A) A sample of 106 customers shows that 55% of them have a pet. Find the standard error for this result, expressed as a decimal rounded to the nearest thousandth. The answer is 0.0483 but I want to know how you get that?

B) You would like an estimate for the mean amount of time a customer spends in your store. A pilot sample has mean 23.5 minutes and standard deviation 8.4 minutes. What sample size is required to have a result within 1.6 minutes of the true mean with a 99% level of confidence? Use 2.576 as the critical z value for 99% confidence. Round UP to the next whole number. The answer is 183 but I want to know how you get that?