电大《试验设计与生物统计》作业二及参考答案小抄.doc

专业好文档试验设计与生物统计作业二（第三到四章）1、什么是变数？变数有哪几种？变数是表示其变异的观察值的总称为变数。变数分为数量变数和质量变数两大类。数量变数又分为连续性变数和间断性变数（又称离散性变数）两类。数量变数是指以数量大小表示的变数，来自对数量性状的测量和计数。连续性变数指通过量长度、测体积或称重量等量测方法所得的数据。其观测值并不限于整数，在两个相邻的数值间可以有微量差异的其它数值存在。常见的连续性变数有作物的株高、穗长、叶面积、穗粒重、产量等。间断性变数（或离散型变数）是以计数的方式获得的数据。其观察值只能以整数表示，如水稻基本苗数、单株分蘖数、每亩成穗数、每穗小穗数、单株粒数、花瓣数、单株分枝数、主茎叶片数等都只能是整数。质量变数又称属性变数，质量变数来自对属性性状的观测记载，这类性状只能观察而不能测量。如花的颜色、芒的有无、果实形状的圆扁等。要从这类性状获得数量资料，可采用下列两种方式：计数，即在一定范围内计数具有该种性状和不具有该种性状的个体数，这种通过计数的方法获得的资料又称次数资料。质量性状数量化。如小麦芒性可分为无芒、短芒与长芒三类，若用0表示无芒，用1表示短芒，用2表示长芒，则从质量性状上获得了数量化的记载，就可得到和数量性状相似的资料。2、什么是总体、样本、参数、统计量？总体是指一个统计问题研究对象的全体，它是具有某种（或某些）共同特征的元素的集合。参数是描述总体特征的数，如反映数据的集中趋势的总体平均数、反映数据的变异程度的总体方差、反映不同总体的相关关系的相关系数等。样本是从总体中抽取的部分个体组成的集团，是总体的代表。由样本所有个体计算出来的特征数称为统计数。统计数是随样本个体组成不同而变化的，是一个变量。3、什么是算术平均数？有何特征和优缺点？算术平均数：是指资料中各观测值的总和除以观测值个数所得的商，简称平均数或均数，记为。算术平均数的特征：算术平均数大小受每个值的影响。如果是n1个数的平均数，是n2个数的平均数，那么全部n1+n2个数的算术平均数是加权平均数：。各观察值与平均数之差（离均差）的总和等于0。离均差平方和最小。若A为任意常数：当=X±A,则； 当=X.A时，,则；当=X/A,则。平均数是有单位的数值，其单位的数值，其单位与原资料相同。算术平均数优点是计算简单，而缺点是计算平均数时没有考虑到近期的变动趋势，因而预测值与实际值往往会发生较大的误差。 4、如何编制次数分布表？编制次数分布表的步骤：求全距：全距是指一批数据中最大值与最小值之间的差距，又称极差。定组数：就是要确定把整批数据划分为多少个等距的区组。定组距:以全距和组数来确定分组的组距。一般原则是取奇数或5的倍数，如1，3，5，7，9，10等。写出组限：为了确定各个观察值的归属，每组必须设有界限。组限是每个组的起止点界限，最小值称为下限，最大值称为上限。求组中值：组中值是各组的组中点在量尺上的数值，其计算公式为：组中值=（组实上限+组实下限）÷2。不同的组距以及不同的组限，必然会产生不同的组中值。如果希望每组的组中值恰好为整数便于后续运算，那么，组距选择为奇数是最好的。编制次数分布表：参照如下次数分布表组别组限组中值次数16.9,7.57.2127.5,8.17.848.1,8.78.455、正态总体的抽样分布的特征？（1） 从一个正态总体抽取的样本，无论样本容量大或小，其样本平均数的抽样分布必为正态分布，具有平均数和方差，记为N(, )。（2）从一个非正态总体抽取的样本，不一定服从正态分布，但当样本容量n增大时，从该总体抽出的样本其平均数的抽样分布趋近于正态分布，具平均数和方差，这就是统计学的中心极限定理。 6、如何运用标准正态分布计算概率？根据中心极限定理，无论原总体分布是否为正态分布，只要样本容量足够大，其的分布都可看作正态分布。在实际应用上，只要n30就可以应用这一定理。知道了抽样分布的规律及其参数，任何样本值的对应的概率就可很容易地计算出来了。平均数的标准化离差分布将转换为u，再查表求概率。 Winger Tuivasa-Sheck, who scored two tries in the Kiwis' 20-18 semi-final win over England, has been passed fit after a lower-leg injury, while Slater has been named at full-back but is still recovering from a knee injury aggravated against USA.Both sides boast 100% records heading into the encounter but Australia have not conceded a try since Josh Charnley's effort in their first pool match against England on the opening day.Aussie winger Jarryd Hayne is the competition's top try scorer with nine, closely followed by Tuivasa-Sheck with eight.But it is recently named Rugby League International Federation player of the year Sonny Bill Williams who has attracted the most interest in the tournament so far.The Kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the World Cup in both rugby league and rugby union after triumphing with the All Blacks in 2011."I'd give every award back in a heartbeat just to get across the line this weekend," said Williams.The (lack of) air up there Watch mCayman Islands-based Webb, the head of Fifa's anti-racism taskforce, is in London for the Football Association's 150th anniversary celebrations and will attend City's Premier League match at Chelsea on Sunday."I am going to be at the match tomorrow and I have asked to meet Yaya Toure," he told BBC Sport."For me it's about how he felt and I would like to speak to him first to find out what his experience was."Uefa has opened disciplinary proceedings against CSKA for the "racist behaviour of their fans" during City's 2-1 win.Michel Platini, president of European football's governing body, has also ordered an immediate investigation into the referee's actions.CSKA said they were "surprised and disappointed" by Toure's 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 descent 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 the 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 boundary 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.They blew it in 2008 when they got caught cold in the final and they will not make the same mistake against the Kiwis in Manchester.Five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by England's Josh Charnley in the opening game of the tournament.That could be classed as a weakness, a team under-cooked - but I have been impressed by the Kangaroos' focus in their games since then.They have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. They've been great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.It is as though their entire tournament has been preparation for the final.In Johnathan Thurston, Cooper Cronk, Cameron Smith and either Billy Slater or Greg Inglis at full-back they have a spine that is unmatched in rugby league. They have played in so many high-pressure games - a priceless asset going into Saturday.The Kiwis are a lot less experienced but winning a dramatic match like their semi-final against England will do wonders for their confidence.They defeated Australia in the Four Nations final in 2010 and the last World Cup, and know they can rise to the big occasion.