8.8 The quality control manager at a lightbulb factory needs to estimate the mean life of a large shipment of lightbulbs. The standard deviation is 100 hours. A random sample of 64 lightbulbs a sample mean life of 350 hours.
a. Construct a 95% confidence interval estimate of the population mean life of lightbulbs in this shipment.
2. 根据《管理科学季刊》所报导的一项研究（Administrative Science Quarterly, June 1988）pilot,公司总经理与副总经理之间的薪金差距往往非常大，而这种差距看来正使公司雇佣更多的副总经理。从商业周刊的“abc字母歌德威英国国际学校经理报酬排行榜”德国学校抽选了105家美国公司作样本，根据来自样本
的数据，平均一家公司所雇佣的副总经理数x=19.4，标准差s=10.1。试在此项信息的基础上，用99%置信区间估计美国公司副总经理的真正平均数。
3. 百度实物翻译>tic tocDuring June and July of 2001, the European Union Executive Commission conducted a study of 6,543 European adults. Of tho surveyed, 56% said that the euro single currency would promote economic growth and 73% knew the correct date of the changeover. Construct a 95% confidence interval estimate for the proportion of European adults who believe that the euro would promote economic growth.
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教师节祝福4. The following data reprent the bounced check fee in dollars for a sample of 23 banks for direct-deposit customers who maintain a $100 balance.
26 28 20 20 21 22 25 25 18 25 15 20 18 20 25 25 22 30 30 30 15 20 29
a. Construct a 95% confidence interval for the population mean bounced check fee.
cctv全称b. Interpret the interval constructed in (a).
