XÉèXµÄ·Ö²¼ÂÉΪP012,Æä·Ö²¼º¯ÊýF(x),Ôò0.30.50.2F(1.5)____.
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1¡¢ÒÑÖªP(A)?0.5, P(AB)?0.2, P(B)?0.4, Çó
(1) P(AB); (2) P(A?B); (3) P(A?B); (4) P(AB).
½â (1) ÒòΪAB?AB?B, ÇÒABÓëABÊDz»ÏàÈݵÄ, ¹ÊÓÐP(AB)?P(AB)?P(B) ÓÚÊÇP(AB)?P(B)?P(AB)?0.4?0.2?0.2;
(2) P(A)?1?P(A)?1?0.5?0.5,
P(A?B)?P(A)?P(AB)?0.5?0.2?0.3;
(3) P(A?B)?p(A)?P(B)?P(AB)?0.5?0.4?0.2?0.7;
(4) P(AB)?P(A?B)?1?P(A?B)?1?0.7?0.3.
2¡¢Ä³³ÇÊÐÖз¢ÐÐ2ÖÖ±¨Ö½A, B. ¾µ÷²é, ÔÚÕâ2ÖÖ±¨Ö½µÄ¶©»§ÖÐ, ¶©ÔÄA±¨µÄÓÐ45%,¶©ÔÄB±¨µÄÓÐ35%, ͬʱ¶©ÔÄ2ÖÖ±¨Ö½A, BµÄÓÐ10%. ÇóÖ»¶©Ò»ÖÖ±¨Ö½µÄ¸ÅÂÊa.£¨
½â ¼ÇÊÂA?{¶©ÔÄA±¨},B?{¶©ÔÄB±¨}, Ôò
{Ö»¶©Ò»ÖÖ±¨}?(A?B)?(B?A)?AB?BA,
ÓÖÕâÁ½¼þÊÂÊÇ»¥²»ÏàÈݵÄ, ÓɸÅÂʼӷ¨¹«Ê½¼°ÐÔÖÊ4, ÓÐ
??P(A?AB)?P(B?AB)?P(A)?P(AB)?P(B)?P(AB)?0.45?0.1?0.35?0.1=0.6. 3¡¢½«±êºÅΪ1, 2, 3, 4µÄËĸöÇòËæÒâµØÅųÉÒ»ÐÐ, ÇóÏÂÁи÷ʼþµÄ¸ÅÂÊ:
(1) ¸÷Çò×Ô×óÖÁÓÒ»ò×ÔÓÒÖÁ×óÇ¡ºÃÅųÉ1, 2, 3, 4µÄ˳Ðò; (2) µÚ1ºÅÇòÅÅÔÚ×îÓұ߻ò×î×ó±ß; (3) µÚ1ºÅÇòÓëµÚ2ºÅÇòÏàÁÚ;
(4) µÚ1ºÅÇòÅÅÔÚµÚ2ºÅÇòµÄÓÒ±ß(²»Ò»¶¨ÏàÁÚ).
½â ½«4¸öÇòËæÒâµØÅųÉÒ»ÐÐÓÐ4!=24ÖÖÅÅ·¨, ¼´»ù±¾Ê¼þ×ÜÊýΪ24. ¼Ç(1), (2),(3), (4)µÄʼþ·Ö±ðΪA,B,C,D.
(1) AÖÐÓÐÁ½ÖÖÅÅ·¨,¹ÊÓÐP(A)?21?. 2412121?. 242(3) ÏȽ«µÚ1,2ºÅÇòÅÅÔÚÈÎÒâÏàÁÚÁ½¸öλÖÃ, ¹²ÓÐ2?3ÖÖÅÅ·¨, ÆäÓàÁ½¸öÇò¿ÉÔÚÆäÓàÁ½¸öλÖÃÈÎÒâÅÅ·Å, ¹²ÓÐ2! ÖÖÅÅ·¨, Òò¶øCÓÐ2?3?2?12ÖÖÅÅ·¨, ¹ÊP(C)?12/24?1/2.
(2) BÖÐÓÐ2?(3!)?12ÖÖÅÅ·¨, ¹ÊÓÐP(B)?(4) µÚ1ºÅÇòÅÅÔÚµÚ2ºÅÇòµÄÓұߵÄÿһÖÖÅÅ·¨, ½»»»µÚ1ºÅÇòºÍµÚ2ºÅÇòµÄλÖñã¶ÔÓ¦ÓÚµÚ1ºÅÇòÅÅÔÚµÚ2ºÅÇòµÄ×ó±ßµÄÒ»ÖÖÅÅ·¨, ·´Ö®ÒàÈ».
Òò¶øµÚ1ºÅÇòÅÅÔÚµÚ2ºÅÇòµÄÓÒ±ßÓëµÚ1ºÅÇòÅÅÔÚµÚ2ºÅÇòµÄ×ó±ßµÄÅÅ·¨ÖÖÊýÏàͬ, ¸÷Õ¼×ÜÅÅ·¨ÊýµÄ1/2, ¹ÊÓÐP(D)?1/2.
13
4¡¢ÉèijÅú²úÆ·ÖÐ, ¼×, ÒÒ, ±ûÈý³§Éú²úµÄ²úÆ··Ö±ðÕ¼45%, 35%, 20%, ¸÷³§µÄ²úÆ·µÄ´ÎÆ·ÂÊ·Ö±ðΪ4%, 2%, 5%, ÏÖ´ÓÖÐÈÎȡһ¼þ,
(1) ÇóÈ¡µ½µÄÊÇ´ÎÆ·µÄ¸ÅÂÊ;
(2) ¾¼ìÑé·¢ÏÖÈ¡µ½µÄ²úƷΪ´ÎÆ·, Çó¸Ã²úÆ·ÊǼ׳§Éú²úµÄ¸ÅÂÊ.
½â ¼ÇʼþA1:¡°¸Ã²úÆ·ÊÇ´ÎÆ·¡±, ʼþA2:¡°¸Ã²úƷΪÒÒ³§Éú²úµÄ¡±, ʼþA3:¡°¸Ã²úƷΪ±û³§Éú²úµÄ¡±, ʼþB:¡°¸Ã²úÆ·ÊÇ´ÎÆ·¡±. ÓÉÌâÉè, Öª
P(A1)?45%,P(A2)?35%,P(A3)?20%,P(B|A1)?4%,P(B|A2)?2%,P(B|A3)?5%,
(1) ÓÉÈ«¸ÅÂʹ«Ê½µÃP(B)??P(A)P(B|A)?3.5%.
iii?13(2) Óɱ´Ò¶Ë¹¹«Ê½(»òÌõ¼þ¸ÅÂʶ¨Òå), µÃ
P(A1B)P(A1)P(B|A1)P(A1|B)???51.4%.
P(B)P(B)5¡¢8Ö§²½Ç¹ÖÐÓÐ5Ö§ÒÑУ׼¹ý£¬3֧δУ׼. Ò»ÃûÉäÊÖÓÃУ׼¹ýµÄǹÉä»÷ʱ£¬ÖаеĸÅ
ÂÊΪ0.8; ÓÃδУ׼µÄǹÉä»÷ʱ£¬ÖаеĸÅÂÊΪ0.3. ÏÖ´Ó8֧ǹÖÐÈÎȡһ֧ÓÃÓÚÉä»÷£¬½á¹ûÖаУ¬ÇóËùÓõÄǹÊÇУ׼¹ýµÄ¸ÅÂÊ.
½â ÉèB1?{ʹÓõÄǹУ׼¹ý}, B2?{ʹÓõÄǹδУ׼}, A?{Éä»÷ʱÖаÐ},ÔòB1,B2ÊÇ
53?µÄÒ»¸ö»®·Ö, ÇÒP(B1)?,P(B2)?,P(A|B1)?0.8,P(A|B2)?0.3.
88P(A|B1)P(B1)40Óɱ´Ò¶Ë¹¹«Ê½, µÃ P(B1|A)??.
P(A|B1)P(B1)?P(A|B2)P(B2)49ÕâÑù, ËùÓõÄǹÊÇУ׼¹ýµÄ¸ÅÂÊΪ
40. 496¡¢¼ÙÉèijµØÇø³ÉÄêÄÐÐÔµÄÉí¸ß(µ¥Î»: ÀåÃ×)X~N(170,7.692), Çó¸ÃµØÇø³ÉÄêÄÐÐÔµÄÉí¸ß³¬¹ý175ÀåÃ׵ĸÅÂÊ.£¨??0.65?0.7422?£©
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5?P{175?X??}?1?P{X?17}5 P{X?17} ?1????175?170???1??(0.65)
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7¡¢ÉèijÏÈü³É¼¨X~N(65, 100)£¬Èô°´²ÎÈüÈËÊýµÄ10%·¢½±£¬ÎÊ»ñ½±·ÖÊýÏßÓ¦ ¶¨Îª¶àÉÙ£¿
½â Éè»ñ½±·ÖÊýÏßΪx0, ÔòÇóʹP{X?x0}?0.1³ÉÁ¢µÄx0.
14
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10??x?65?x?65?¼´??0?1.29, ½âµÃx0?77.9, ¹Ê·ÖÊýÏ߿ɶ¨Îª78·Ö. ??0.9, ²é±íµÃ01010??8ÉèËæ»ú±äÁ¿?X,Y?µÄ¸ÅÂÊÃܶÈΪ
?Ax,0?x?1,0?y?x f?x,y???
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22??8¡¢½â£º £¨1£©ÓÉ??????????f?x,y?dxdy?1¿ÉµÃ£¬
1x10 ?dx?Axdy?1 ¼´
A?1,A?3 31?=?2?1£¨2£©P?X?,Y??2??112dx?3xdy
03 ?9 169¡¢Ä³¹«¹²Æû³µÕ¾´ÓÉÏÎç7ʱÆð, ÿ15·ÖÖÓÀ´Ò»°à³µ, ¼´7:00, 7:15, 7:30, 7:45µÈʱ¿ÌÓÐÆû³µµ½´ï´ËÕ¾, Èç¹û³Ë¿Íµ½´ï´Ëվʱ¼äXÊÇ7:00µ½7:30Ö®¼äµÄ¾ùÔÈËæ»ú±äÁ¿,ÊÔÇóËûºò³µÊ±¼äÉÙÓÚ5·ÖÖӵĸÅÂÊ.
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?1?,0?x?30 X~U(0,30),f(x)??30?ÆäËü?0,Ϊʹºò³µÊ±¼äXÉÙÓÚ5·ÖÖÓ, ³Ë¿Í±ØÐëÔÚ7:10µ½7:15Ö®¼ä, »òÔÚ7:25µ½7:30Ö®¼äµ½´ï
³µÕ¾, ¹ÊËùÇó¸ÅÂÊΪ
P{10?X?15}?P{25?X?30}??1dx?103015?11dx? 2530330¼´³Ë¿Íºò³µÊ±¼äÉÙÓÚ5·ÖÖӵĸÅÂÊÊÇ1/3.
¡¤10¡¢Ä³Ôª¼þµÄÊÙÃüX·þ´ÓÖ¸Êý·Ö²¼, ÒÑÖªÆä²ÎÊý??1/1000, Çó3¸öÕâÑùµÄÔª¼þʹÓÃ1000Сʱ, ÖÁÉÙÒÑÓÐÒ»¸öË𻵵ĸÅÂÊ.
½â ÓÉÌâÉèÖª, XµÄ·Ö²¼º¯ÊýΪ
x??1?e?1000,x?0F(x)??.
?0,x?0?Óɴ˵õ½
P{X?1000}?F?1000??1?e?1
15
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0(1?e?1)0(e?1)3?1?e?3. P{Y?1}?1?P{Y?0}?1?C311¡¢ÉèËæ»ú±äÁ¿XºÍY¾ßÓÐÁªºÏ¸ÅÂÊÃܶÈ
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0,ÆäËü?Çó±ßÔµ¸ÅÂÊÃܶÈfX(x),fY(y).
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fX(x)????????f(x,y)dy?????x2x6dy?6(x?x2),0?x?1,
0,ÆäËüy1y?x2O1y?x?y?fY?(y)?f(x,y)dx??y6dx?6(y?y),0?y?1.
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0 0.1 0.2 0
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(1) ÇóY?0ʱ, XµÄÌõ¼þ¸ÅÂÊ·Ö²¼; (2) ÅжÏXÓëYÊÇ·ñÏ໥¶ÀÁ¢? £¨3£©ÇóF(0,0).
½â (1) P{Y?0}?0.2?0.05?0?0.25,
????xÔÚY?0ʱ, XµÄÌõ¼þ¸ÅÂÊ·Ö²¼Îª
P{X?0|Y?0}?P{X?1|Y?0}?P{X?0,Y?0}0.2??0.8,
P{Y?0}0.25P{X?1,Y?0}0.05??0.2,
P{Y?0}0.25P{X?2,Y?0}0??0,
P{Y?0}0.25P{X?2|Y?0}? (2) ÒòP{X?0}?0.3,P{Y??1}?0.1?0.3?0.15?0.55,
¶øP{X?0,Y??1}?0.1, ¼´P{X?0,Y??1}?P{X?0}P{Y??1} ËùÒÔ, XÓëY²»¶ÀÁ¢.
(3)F(0,0)?P{X?0,Y?0}?P{X?0,Y??1}?0.2?0.1?0.3. 13¡¢ÒÑÖªÀëÉ¢ÐÍËæ»úÏòÁ¿(X,Y)µÄ¸ÅÂÊ·Ö²¼Îª
Y ?1 X 0 0.1 0 0.2 2 0 16