Basic Statistics Exam Answers

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ATENEO DE DAVAO UNIVERSITY E. Jacinto Street, 8000 Davao City 2ND Semester, S.Y. 2014-2015 Math 213: BUSINESS STATISTICS Prelim Examination Name: Adlin joey B. Almencion Score: Rating: Year and Course: 2-MKA PROBLEM SETS: 1) The owner of a gasoline station wants to study gasoline purchasing habits of motorists at his station. He selects a random sample of 60 motorists during a certain week, with the following results: * The amount purchased was X = 11.3 gallons, S = 3.1 gallons. * Eleven motorists purchased premium-grade gasoline. a. At the 0.05 level of significance, is there evidence that the population mean purchase was different from 10 gallons? ANSWER = T-interval for μ n=60 x= 11.3 and s= 3.1(this standard deviation came from the sample) The hypothesis are Ho:μ≤10 H1:μ>10 t = x - x-μsn =11.3-103.160= 3.2483 It should be -1.96 < z <1.96 but since 3.2483 > 1.96 therefore the hypothesis should be rejected. b. At the 0.05 level of significance, is there evidence that less than 20% of all the motorists at the station purchased premium-grade gasoline? ANSWER = The p-value is 2282 , which is not less than σ=.05 c. What is your answer to (a) if the sample mean equals 10.3 gallons? ANSWER = z=(10-11.3)/3.1= -0.42 d. What is your answer to (c) if 7 motorists purchased premium-grade gasoline? ANWERS = μ = 60 2) Online magazines make it easy for readers to link to an advertiser’s website directly from an advertisement placed in the digital magazine. A recent survey indicated that 56% of online magazine readers have clicked on an advertisement and linked directly to the advertiser’s website. The survey was based on a sample size of n = 6,403. e. Use the p-value approach to try to determine whether there is evidence that more than half of all the readers of

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