In an ancient civilization, shaft graves are named for decorated sword shafts that are buried along with bodies. The accompanying table gives the results of one study in which the number of shafts buried at each of 13 grave sites were counted a Estimate the average number of shafts buried in this civilization's graves using a 90% confidence interval. Give a practical interpretation of the interval b. What assumption about the data on shaft graves is required for the inference in part to be valid? Click the icon to view the table of shaft grave data a. The confidence interval is (Type integers or decimals rounded to two decimal places as needed.) Give a practical interpretation of the interval. Select the correct choice below and fill in any answer boxes to complete your choice (Round to two decimal places as needed. Use ascending order) OA we OR W OC wh % confidence, the true mean number of shatta buried in graves is exactly % confidence, the true variance of the number of shahs buried in graves is between % confidence, the true mean number of shafts buried in graves is between and b. Choose the correct answer below OA It must be assumed that the data was selected randomly from a population with an approximately normal distribution OB must be assumed that the data was selected randomly from a population with a continuous probability distribution OC. must be assumed that the data was selected randomly from a population with a uniform distribution OD. There are no assumptions required for the validity of the inference in part a. This will be valid for any data selected Shaft Grave Data 1 34 105 " 5 Print Done