Americans spend nearly $7 billion on halloween costumes and decorations (the wall street journal, october 27, 2011). sample data showing the amount, in dollars, 16 adults spent on a halloween costume are as follows. a. what is the estimate of the population mean amount adults spend on a hallow costume? b. what is the sample standard deviation? c. provide a 95% confidence interval estimate of the population standard de the amount adults spend on a halloween costume?