Tiêu đề ST104b - Statistics 2 - 2015 Examiners Commentaries.pdf ✅

Examiners’ commentaries 2015 Examiners’ commentaries 2015 ST104b Statistics 2 Important note This commentary reflects the examination and assessment arrangements for this course in the academic year 2014–15. 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. General remarks Learning outcomes At the end of this half course, and having completed the Essential reading and activities, you should be able to: • apply and be competent users of standard statistical operators and be able to recall a variety of well-known distributions and their respective moments • explain the fundamentals of statistical inference and apply these principles to justify the use of an appropriate model and perform tests in a number of different settings • demonstrate understanding that statistical techniques are based on assumptions and the plausibility of such assumptions must be investigated when analysing real problems. Format of the examination The examination is 2 hours long and you must answer all four questions. Question 1 for 40% of the marks is a compulsory question with several parts. It is designed to test general knowledge and understanding of the whole syllabus. Here candidates are expected to give reasoned answers, with some explanation, avoiding one-word responses which will never be given any marks. More emphasis is given to understanding than to knowledge. The other three questions are compulsory too and account for 60% in total. They are meant to test a greater depth of knowledge on parts of the syllabus. They are also longer and examine the ability to apply general knowledge and concepts to specific problems. 1


ST104b Statistics 2 Examiners’ commentaries 2015 ST104b Statistics 2 Important note This commentary reflects the examination and assessment arrangements for this course in the academic year 2014–15. 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 parts of question 1 (40 marks in total). Question 1 (a) Consider a sequence of random variables X1, X2, X3, . . . that are independent and normally distributed with mean 0 and variance 1. Using as many of these random variables as you like construct a random variable that is a function of X1, X2, X3, . . . and has a t distribution with 11 degrees of freedom. Any correct answer will be given full marks. You do not have to think of the smallest number of random variables that make this possible. (5 marks) Reading for this question Section 6.11.2 of the subject guide defines the (Student’s) t distribution as a standard normal variable divided by the square root of an independent chi-squared variable divided by its degrees of freedom. 4