電大《試驗設計與生物統(tǒng)計》作業(yè)二及參考答案小抄

1、專業(yè)好文檔試驗設計與生物統(tǒng)計作業(yè)二（第三到四章）1、什么是變數？變數有哪幾種？變數是表示其變異的觀察值的總稱為變數。變數分為數量變數和質量變數兩大類。數量變數又分為連續(xù)性變數和間斷性變數（又稱離散性變數）兩類。數量變數是指以數量大小表示的變數，來自對數量性狀的測量和計數。連續(xù)性變數指通過量長度、測體積或稱重量等量測方法所得的數據。其觀測值并不限于整數，在兩個相鄰的數值間可以有微量差異的其它數值存在。常見的連續(xù)性變數有作物的株高、穗長、葉面積、穗粒重、產量等。間斷性變數（或離散型變數）是以計數的方式獲得的數據。其觀察值只能以整數表示，如水稻基本苗數、單株分蘗數、每畝成穗數、每穗小穗數、單株粒數、

2、花瓣數、單株分枝數、主莖葉片數等都只能是整數。質量變數又稱屬性變數，質量變數來自對屬性性狀的觀測記載，這類性狀只能觀察而不能測量。如花的顏色、芒的有無、果實形狀的圓扁等。要從這類性狀獲得數量資料，可采用下列兩種方式：計數，即在一定范圍內計數具有該種性狀和不具有該種性狀的個體數，這種通過計數的方法獲得的資料又稱次數資料。質量性狀數量化。如小麥芒性可分為無芒、短芒與長芒三類，若用0表示無芒，用1表示短芒，用2表示長芒，則從質量性狀上獲得了數量化的記載，就可得到和數量性狀相似的資料。2、什么是總體、樣本、參數、統(tǒng)計量？總體是指一個統(tǒng)計問題研究對象的全體，它是具有某種（或某些）共同特征的元素的集合。參

3、數是描述總體特征的數，如反映數據的集中趨勢的總體平均數、反映數據的變異程度的總體方差、反映不同總體的相關關系的相關系數等。樣本是從總體中抽取的部分個體組成的集團，是總體的代表。由樣本所有個體計算出來的特征數稱為統(tǒng)計數。統(tǒng)計數是隨樣本個體組成不同而變化的，是一個變量。3、什么是算術平均數？有何特征和優(yōu)缺點？算術平均數：是指資料中各觀測值的總和除以觀測值個數所得的商，簡稱平均數或均數，記為。算術平均數的特征：算術平均數大小受每個值的影響。如果是n1個數的平均數，是n2個數的平均數，那么全部n1+n2個數的算術平均數是加權平均數：。各觀察值與平均數之差（離均差）的總和等于0。離均差平方和最小。若a為

4、任意常數：當=xa,則； 當=x.a時，,則；當=x/a,則。平均數是有單位的數值，其單位的數值，其單位與原資料相同。算術平均數優(yōu)點是計算簡單，而缺點是計算平均數時沒有考慮到近期的變動趨勢，因而預測值與實際值往往會發(fā)生較大的誤差。 4、如何編制次數分布表？編制次數分布表的步驟：求全距：全距是指一批數據中最大值與最小值之間的差距，又稱極差。定組數：就是要確定把整批數據劃分為多少個等距的區(qū)組。定組距:以全距和組數來確定分組的組距。一般原則是取奇數或5的倍數，如1，3，5，7，9，10等。寫出組限：為了確定各個觀察值的歸屬，每組必須設有界限。組限是每個組的起止點界限，最小值稱為下限，最大值稱為上限。

5、求組中值：組中值是各組的組中點在量尺上的數值，其計算公式為：組中值=（組實上限+組實下限）2。不同的組距以及不同的組限，必然會產生不同的組中值。如果希望每組的組中值恰好為整數便于后續(xù)運算，那么，組距選擇為奇數是最好的。編制次數分布表：參照如下次數分布表組別組限組中值次數16.9,7.57.2127.5,8.17.848.1,8.78.455、正態(tài)總體的抽樣分布的特征？（1） 從一個正態(tài)總體抽取的樣本，無論樣本容量大或小，其樣本平均數的抽樣分布必為正態(tài)分布，具有平均數和方差，記為n(, )。（2）從一個非正態(tài)總體抽取的樣本，不一定服從正態(tài)分布，但當樣本容量n增大時，從該總體抽出的樣本其平均數的抽

6、樣分布趨近于正態(tài)分布，具平均數和方差，這就是統(tǒng)計學的中心極限定理。 6、如何運用標準正態(tài)分布計算概率？根據中心極限定理，無論原總體分布是否為正態(tài)分布，只要樣本容量足夠大，其的分布都可看作正態(tài)分布。在實際應用上，只要n30就可以應用這一定理。知道了抽樣分布的規(guī)律及其參數，任何樣本值的對應的概率就可很容易地計算出來了。平均數的標準化離差分布將轉換為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

7、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 charnleys effort in their first pool match against england on the o

8、pening day.aussie winger jarryd hayne is the competitions 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

9、 - 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.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air

10、 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 toure, h

11、e 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 body, has

12、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 descent could

13、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 atmos

14、phere (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

15、(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 n

16、ot 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 englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team un

17、der-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. theyve been great at all the unglam

18、orous 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 asse