电大工程数学作业4答案

1、专业好文档工程数学作业（第四次）第6章 统计推断（一）单项选择题 设是来自正态总体（均未知）的样本，则（a）是统计量 a. b. c. d. 设是来自正态总体（均未知）的样本，则统计量（d）不是的无偏估计 a. b. c. d. （二）填空题 1统计量就是 不含未知参数的样本函数 2参数估计的两种方法是 点估计 和 区间估计 常用的参数点估计有 矩估计法 和 最大似然估计 两种方法 3比较估计量好坏的两个重要标准是 无偏性 ， 有效性 4设是来自正态总体（已知）的样本值，按给定的显著性水平检验，需选取统计量 5假设检验中的显著性水平为事件（u为临界值）发生的概率 （三）解答题 1设对总体得到一

2、个容量为10的样本值4.5, 2.0, 1.0, 1.5, 3.5, 4.5, 6.5, 5.0, 3.5, 4.0试分别计算样本均值和样本方差解： 2设总体的概率密度函数为试分别用矩估计法和最大似然估计法估计参数 解：提示教材第214页例3矩估计：最大似然估计：， 3测两点之间的直线距离5次，测得距离的值为（单位：m）：108.5 109.0 110.0 110.5 112.0测量值可以认为是服从正态分布的，求与的估计值并在；未知的情况下，分别求的置信度为0.95的置信区间解： （1）当时，由10.95， 查表得： 故所求置信区间为： （2）当未知时，用替代，查t (4, 0.05 ) ，得

3、 故所求置信区间为：4设某产品的性能指标服从正态分布，从历史资料已知，抽查10个样品，求得均值为17，取显著性水平，问原假设是否成立 解：，由 ，查表得：因为 1.96 ，所以拒绝 5某零件长度服从正态分布，过去的均值为20.0，现换了新材料，从产品中随机抽取8个样品，测得的长度为（单位：cm）：20.0, 20.2, 20.1, 20.0, 20.2, 20.3, 19.8, 19.5问用新材料做的零件平均长度是否起了变化（）解：由已知条件可求得： | t | 2.62 接受h0即用新材料做的零件平均长度没有变化。if we dont do that it will go on and go

4、 on. we have to stop it; we need the courage to do it.his comments came hours after fifa vice-president jeffrey webb - also in london for the fas celebrations - said he wanted to meet ivory coast international toure to discuss his complaint.cska general director roman babaev says the matter has been

5、 exaggerated by the ivorian and the british media.blatter, 77, said: it has been decided by the fifa congress that it is a nonsense for racism to be dealt with with fines. you can always find money from somebody to pay them.it is a nonsense to have matches played without spectators because it is aga

6、inst the spirit of football and against the visiting team. it is all nonsense.we can do something better to fight racism and discrimination.this is one of the villains we have today in our game. but it is only with harsh sanctions that racism and discrimination can be washed out of football.the (lac

7、k of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya

8、 toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing b

9、ody, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska.baumgartner the disappointing news: mission aborted.the supersonic descen

10、t could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of t

11、he atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundar

12、y layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.below, the earth becomes the concrete bottom of a swimming pool tha

13、t he wants to land on, but not too hard. still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. it will be like he is diving into the shallow end.skydiver preps for the big jumpwhen he jumps, he is expected to reach the speed of sound - 690 mp

14、h (1,110 kph) - in less than 40 seconds. like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to earth. but this will not be enough to stop him completely.if he goes too fast or spins out of control, he has a stabilization parachute that can be deployed

15、 to slow him down. his team hopes its not needed. instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).in order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). he will have a reserve parachute that will open automatically if he loses consciousn