1. During a university orientation event, incoming students are advised about the cost of textbooks for a typical study period. Students are told that the average student spends $280 per study period on books. Based on your own experience you feel that this is an *under*-estimate of the true expenditure. You ask 30 of your friends and you obtain the following textbook expenditure amounts (in dollars):

** **

264 |
286 |
297 |
295 |
298 |
303 |
308 |
312 |
319 |
327 |

283 |
289 |
291 |
298 |
299 |
304 |
310 |
313 |
324 |
327 |

284 |
291 |
294 |
298 |
300 |
304 |
312 |
315 |
326 |
331 |

(a) Use EXCEL to find the sample mean. Suppose that the population standard deviation for the cost of textbooks is known to be $15.50. Construct a 95% confidence interval for the true population mean cost of textbooks. Do you have evidence to tell the university that their statement is inaccurate? Does the population cost of textbooks have to be Normally distributed here? Explain.

(b) What sampling method did you use? Was it a good choice? Explain.

(c) If the true average cost of textbooks per study period is $280 as the university claims, what is the probability of a mean cost of textbooks above $290 for a sample of 30 students? Assume that the population standard deviation is $15.50. Use a diagram!

2. A printer cartridge is reported by the manufacturer to have an average life span of 2,500 pages. A random sample of twenty-five cartridges used in a variety of printers in a company found that the mean life span was 2,410 pages with a standard deviation of 220 pages. Do you believe the company’s claim? Test at a = 0.05.

Subject | Business |

Due By (Pacific Time) | 11/01/2014 02:00 am |

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