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. N 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. KO