stat101-hw7-solution - Solutions for STAT 101, Homework 7...

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Professor Rakhlin Solutions prepared by Julie, Tung, and Wei November 17, 2011 Problem 1 (Chapter 13 problem 12) [2 points] The size of the sample survey should be a fixed percentage of the population size in order to produce representative results. Answer False. The survey size is fixed, not a given percentage. Problem 2 (Chapter 13 problem 16) [2 points] Randomization produces samples that mimic the various characteristics of the population without systematic bias. Answer True. Problem 3 (Chapter 13 problem 22) [6 points] PC Magazine asks all of its readers to participate in a survey of their satisfaction with different brands of computer systems and peripherals. In the 2004 survey, more than 9,000 readers rated the products on a scale from 1 to 10. The magazine reported that the average rating assigned by 222 readers to a Kodak compact digital camera was 7.5 Answer a) Population : Readers of PC Magazine ( a better population would be all computer users, as represented by those who read this magazine) b) Parameter: Mean rating of Kodak digital camera. c) Sampling frame: Anyone reading the issue soliciting participation d) Sample size: 225 ( for the camera, others did not rate it) e) Sample design: Voluntary response. f) Other issues: One might suspect that only those who were particularly pleased or displeased with their camera participate. One point for each correct answer. Problem 4 (Chapter 13 problem 28) [ 4 points] Four new sampling strategies have been proposed to help the bank in Exercise 27 determine whether customers favor opening on Saturdays versus keeping branches open longer during the week. For each, indicate what kind of sampling strategy is involved and what biases might result. a) Sponsor a commercial during a TV program, asking people to dial one of two phone numbers to indicate which option they prefer. 1
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This note was uploaded on 04/04/2012 for the course STAT 101 taught by Professor Heller during the Fall '08 term at UPenn.

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stat101-hw7-solution - Solutions for STAT 101, Homework 7...

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