doko.vn-199055-Tong-quan-kinh-te-luong

Khi o ta ch co the c lng gia tr trung bnh cua bien

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Unformatted text preview: 152 1/7 157 1/7 160 1/7 162 1/7 113 125 137 149 137 1/6 145 1/6 155 1/6 165 1/6 175 1/6 189 1/6 150 1/7 152 1/7 175 1/7 178 1/7 180 1/7 185 1/7 191 1/7 161 173 20 Coâng thöùc kyø voïng coù ñieàu kieän: ng n: E(Y/X=Xi)=E(Y/Xi) = y .P Y y /X X j j i j Nhö vaäy: E(Y/X=80) = 55 1 +60 1 +65 1 +70 1 +75 1 5 5 5 5 5 1 (55+60+65+70+75) = 65 =Y . = 80 5 Töông töï, E(Y/X=100)=65. 1 +70. 1 +74. 1 +80. 1 +85. 1 6 6 6 6 6 +88. 1 = 1 (65+70+74+80+85+88)=77= Y . 100 66 Do ñoù ta coù keát quaû toång quaùt: E (Y / X ) Y . i X i 16/12/2006 21 • Vaäy coù theå xem E(Y/Xi) laø moät haøm naøo ñoù cuûa bieán giaûi thích Xi , bieåu dieãn nhö sau: • E(Y/Xi) = f(Xi) • vaø ñöôïc goïi laø “haøm hoài quy toång theå xaùc ñònh – PRF”. PRF (Population Regression Function) cho bieát giaù trò trung bình cuûa Y seõ thay ñoåi nhö theá naøo khi X nhaän caùc giaù trò khaùc nhau. Neáu PRF coù moät bieán ñoäc laäp thì goïi laø hoài quy ñôn (hoài quy hai bieán), PRF coù töø hai bieán ñoäc laäp tr...
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