1、 1 2.6 1. .2. ( ) ( 2 2 ) ( 3 3 ) .3. 1 P(x) _ ( 0 R) 2 (1) x _ x _ (2) _ (3) _ _ (4) x _ 3 X _ _ X 2 _ 4 3 N( 2 ) X _ 3 X ( ) 68.3%. ( 2 2 ) 95.4%. ( 3 3 ) 99.7%. 5 P(x) 1 e (x ) 2 2 2 x R X _ 2 X _ X _ 1 f(x) f(x) 1 (x 10) 2 8 _ _. 2 X N(0 2 ) P( 2 X 0) 0.4 P(X2) _ 3 N(4 2 ) P( 4) _. 4 X N(170,7 2
2、 )( cm) 99.7% 170 cm _ 5 4 _ ( ) x x x x0) (0,1) 0.4 (0,2) _ 8 N( 2 ) 1 000 ( 3 3 ) _ 9 10 N(90 100) (1) (70,110) (2) 2 000 (80,100) 3 11 X N( 2 ) P(X ) _. 12 N(70,10 2 ) 60 (1) (2) 80 90 1 2 3 P( 2) 1 2 (1 0.4 2) 0.1. 3. 1 24 4 P( 4) 1 2 . 4 (149,191) 5 6 7 0.8 x 1 (1,2) 0.4. 8 3 ( 3 3 ) 0.997 1 00
3、0 997 3 9 x 20 1 2 20 1 1 2 2. (x) 1 2 e (x 20) 2 4 x R. 20 2 ( 2) 2 2. 10 N(90,100) 90 100 10. (1) ( 2 2 ) 0.954 2 90 2 10 70 2 90 2 10 110 (70,110) 0.954. (2) 90 10 80 100. ( ) 0.683 (80,100) 0.683. 2 000 (80,100) 2 000 0.683 1 366( ) 11. 1 2 X N( 2 ) x P(x ) 1 2 . 12 (1) X X N(70,10 2 ) 70 10. 60 80 P(70 10X 70 10) 0.683 1 2 (1 0.683) 0.158 5 15.85%. (2) 80 90 1 2 P(70 X 70 P(60x 80) 1 2 (0.954 0.683) 0.135 5. 80 90 13.55%.
