Question

In an ancient civilization, shaft graves are named for decorated sword shafts that are buried along with bodies. The accompanying table gives the resuits of one study in which the number of shafts buried at each of 130 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 a 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 corect choice below and il in any answer boxes to complete your choice. (Round to two decimal places as needed. Use ascending order) OA With % confidence, the true mean number of shafts buried in graves is exactly % confidence, the true mean number of shafts buried in graves is between I OB Wth and O C. wth % confidence, the true variance of the number of shats buried in graves is between and b. Choose the corect answer below OA Bmust be assumed that the data was selected randomly from a population with a continuous probablity distrbution OB. tmust be assumed that the data was selected randomly from a population with an appeoximately nomal distribution OC It must be assumed that the data was selected randomly from a population with a undorm distribution OD. There are no assumptions required for the validty of the inference in part a This will be vald for any data selected.

Answer 1

Here we have: 3.231 S 2.127 n 13 a 1-0.90 0.10 (90% confidence level) df n-1 13-1 12 wwww Critical value: tarit taidf to.10/2/12 = +1.782 a) Confidence interval: μ=I + t.

2.127 - 3.231 t 1.782 V13 = 3.231 t 1.051 2.18 < u< 4.28 Correct option "B" With 90% confidence, the true mean number of shaft buried in graves is between 2.18 and 4.28 b) Correct option "B" It must be assume that the data was selected randomly from a population with an approximately normal distribution