(2008•威海)甲,乙兩支儀仗隊(duì)隊(duì)員的身高(單位:厘米)如下:
甲隊(duì):178,177,179,178,177,178,177,179,178,179;
乙隊(duì):178,179,176,178,180,178,176,178,177,180;
(1)將下表填完整:
身高176177178179180
甲隊(duì)(人數(shù))34
乙隊(duì)(人數(shù))211
(2)甲隊(duì)隊(duì)員身高的平均數(shù)為______厘米,乙隊(duì)隊(duì)員身高的平均數(shù)為______厘米;
(3)你認(rèn)為哪支儀仗隊(duì)更為整齊?簡(jiǎn)要說(shuō)明理由.
【答案】分析:根據(jù)平均數(shù)和方差的概念求平均數(shù)和方差,哪支儀仗隊(duì)更為整齊可通過(guò)方差進(jìn)行比較.
解答:解:(1)
身高176177178179180
甲隊(duì)(人數(shù))343
乙隊(duì)(人數(shù))21412
(2)=(3×177+4×178+3×179)=178,
=(2×176+1×177+4×178+1×179+2×180)=178.

(3)甲儀仗隊(duì)更為整齊.
理由如下:
s2=[3(177-178)2+4(178-178)2+3(179-178)2]=0.6;
s2=[2(176-178)2+(177-178)2+4(178-178)2+(179-178)2+2(180-178)2]=1.8;
因?yàn)榧,乙兩支儀仗隊(duì)隊(duì)員身高數(shù)據(jù)的方差分別為0.6和1.8,
因此,可以認(rèn)為甲儀仗隊(duì)更為整齊.
(也可以根據(jù)甲,乙兩隊(duì)隊(duì)員身高數(shù)據(jù)的極差分別為2厘米,4厘米判斷).
點(diǎn)評(píng):考查了平均數(shù)和方差在現(xiàn)實(shí)中應(yīng)用.
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