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a) A random sample of computer accessories is chosen for comparing price quoted by two suppliers (namely A and B), with quoted price ($) listed below: Accessory 1 2 3 4 5 6 7 8 Supplier A 450 100 280 800 160 200 360 1400 Supplier B 400 120 290 750 150 210 340 1450 Test whether the mean price quoted by suppliers A and B are the same at 5% level of significance. [8 marks] b) The career officer of a university is studying the monthly salary of alumni after graduating for 10 years. Random samples of alumni graduated from Faculty A and B are chosen with summaries provided below: Faculty Sample size Mean Standard deviation A 20 $62000 $14500 B 22 $60000 $18300 Can the career officer conclude that the mean monthly salary of all alumni graduated from Faculty A is higher than that of Faculty B at 5% level of significance? State your assumptions. [8 marks] c) A retail shop sells 4 brands of mobile phones. Sales manager claims that the popularities among these 4 brands of mobile phones in the last quarter were the same. A random sample of sales records in the last quarter is chosen and the number of mobile phones sold for the individual brands are listed below: Brand A B C D No. of mobile phones sold 38 52 44 66 Test for the sales manager's claim at 10% level of significance. [6 marks]