In 2017, Americans spent a record-high $9.1 billion on Halloween-related purchases (the balance website). Sample data showing the amount, in dollars, 16 adults spent on a Halloween costume are as follows. 10 69 23 67 36 39 32 45 50 17 15 96 48 33 63 29 a. What is the estimate of the population mean amount adults spend on a Halloween costume (to 2 decimals)? $ b. What is the sample standard deviation (to 2 decimals)? $ c. Provide a 95% confidence interval estimate of the population standard deviation for the amount adults spend on a Halloween costume (to 2 decimals). Use Table 11.1. $