Tiêu đề ST104b - Statistics 2 - 2018 Examiners Commentaries.pdf ✅

ST104b Statistics 2 Examiners’ commentaries 2018 ST104b Statistics 2 Important note This commentary reflects the examination and assessment arrangements for this course in the academic year 2017–18. The format and structure of the examination may change in future years, and any such changes will be publicised on the virtual learning environment (VLE). Information about the subject guide and the Essential reading references Unless otherwise stated, all cross-references will be to the latest version of the subject guide (2014). You should always attempt to use the most recent edition of any Essential reading textbook, even if the commentary and/or online reading list and/or subject guide refer to an earlier edition. If different editions of Essential reading are listed, please check the VLE for reading supplements – if none are available, please use the contents list and index of the new edition to find the relevant section. Comments on specific questions – Zone A Candidates should answer all FOUR questions: QUESTION 1 of Section A (40 marks) and all THREE questions from Section B (60 marks in total). Candidates are strongly advised to divide their time accordingly. Section A Answer all fout parts of question 1 (40 marks). Question 1 (a) For each one of the statements below say whether the statement is true or false, explaining your answer. Throughout this question A and B are events such that 0 < P (A) < 1 and 0 < P (B) < 1. i. If A and B are independent, then P (A) + P (B) > P (A ∪ B). ii. If P (A | B) = P (A | Bc ) then A and B are independent. iii. If A and B are disjoint events, then Ac and Bc are disjoint. iv. Let S and T be unbiased estimators for the parameter θ. Then ST is an unbiased estimator for θ 2 . v. The power of a test is the probability the alternative hypothesis is false. (10 marks) Reading for this question For i. and iii. see basic properties of probability in Section 2.7 of the subject guide; for ii., see conditional probability in Section 2.9; for iv., see Section 7.6; for v., see Section 9.10. 4