设随机变量X~B(n,0.2),且D(0.5X-1)=0.32,则n等于多少
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\u7531\u9898\u610f\u5f97
u=3\uff0c\u03c3=1
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P\uff08-1\uff1cx\uff1c1\uff09
=fai\uff081-3\uff09/1-fai\uff08-1-3\uff09/1
=fai\uff08-2)-fai\uff08-4\uff09
\u518d\u6839\u636e\u67e5\u8868\uff0c\u5c31\u53ef\u4ee5\u5f97\u5230
P\u7684\u503c\u4e86
绛旓細鐢卞凡鐭ワ紝DX=n*0.2*0.8=0.16n,鑰孌(0.5X-1)=0.5^2DX=0.25DX=0.25*0.16n=0.32,鍗冲彲姹俷
绛旓細浣犲ソ锛闅忔満鍙橀噺X~B(10,0.2),Y~e(0.5),鍒欐湁EX=10*0.2=2锛孍Y=1/0.5=2锛屾墍浠(4X-3Y)=4EX-3EY=2銆傜粡娴庢暟瀛﹀洟闃熷府浣犺В绛旓紝璇峰強鏃堕噰绾炽傝阿璋紒
绛旓細鐢变簬鏄闅忔満鍙橀噺X~B锛屾墍浠ョ洿鎺ュ鍏紡锛欵(x)=np=10*0.2銆
绛旓細X~b(n,p)鏈嶄粠浜岄」鍒嗗竷锛屽垯E(X)=np E(3x-2)=3Ex-2=3*10*0.2-2=4
绛旓細鐢变簬X~B(100,0.2)锛孍X=100脳0.2=20锛孌X=100脳0.2脳0.8=16锛岀敱涓績鏋侀檺瀹氱悊鍙煡X鐨杩戜技鍒嗗竷涓篨~N(20,16)锛屾墍浠(X-20)/4~N(0,1)锛屾墍浠(20鈮鈮30)=P(0鈮(X-20)/4鈮2.5)=桅(2.5)-桅(0)=0.9938-0.5=0.4938銆
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绛旓細瑙 E(X)=100*0.2=20,D(X)=100*0.2*0.8=16 浜庢槸鐢变腑蹇冩瀬闄愬畾鐞嗗緱
绛旓細D(X)=np锛1-p锛=3*0.2*(1-0.2)=0.48 瑙i鎬濊矾锛氱敱浜嶺-B(3,0.2)鏈嶄粠浜岄」鍒嗗竷锛屾墍浠=3锛宲=0.2 鎵浠ワ紝D(X)=np锛1-p锛=3*0.2*(1-0.2)=0.48 濡傛灉X-B(n,p)锛堜篃灏辨槸璇达紝X鏄湇浠庝簩椤瑰垎甯冪殑闅忔満鍙橀噺锛夛紝閭d箞X鐨鏂瑰樊D(X)=np锛1-p锛夈
绛旓細x鏈嶄粠浜岄」鍒嗗竷锛氭墍浠锛圷=4锛=P锛坸=2锛=3*0.2²*0.8=0.096
绛旓細绛旀鏄疌锛屼笅鍥炬槸璁$畻杩囩▼銆傜粡娴庢暟瀛﹀洟闃熷府浣犺В绛旓紝璇峰強鏃堕噰绾炽傝阿璋紒