2.2. PHl/ONG PHAP NGHIEN CUU
2.2.2. L Phuong phap dieu tra thu thap thong tin
3.2.2.3. Phuong phap phan tich thong tin
- Phuong phap phan to: Phan to la phan chia cac don vj dieu tra vao cac td (va cac tieu td) theo cac khoang cach to da duoc dinh san. Su dung phuong phap phan to de tim ra xu hudng tac dong cua cac yeu to nguyen nhan den yeu to ket qua.
M6i to se bao g6m cac don vj dieu tra co cung chung mot tmh chat theo tieu thu'c phan to nao do. Khoang cach to la do rong cua cac td. Trong luan van, cac tieu thu'c dung de phan to la: quy mo dien tich, loai hinh san xuat, gia trj gia tang.
Sau khi phan chia cac don vj tong the vao cac to, ta se tmh ra gia trj binh quan cua cac tieu thuc ket qua hay hieu qua kinh doanh. So sanh cac gia trj binh quan nay, se thay duoc anh huong bien dong cua tieu thu'c phan to tdi su thay doi trong gia trj cua tieu thurc ket qua. Dd kiem djnh do tin cay thong ke cua sir thay doi nay, trong trudng hop so don vj tong the cua mot hoac ca hai to <30, ta co the dung kiem djnh t (t-Test). Tham so t dung de kiem djnh (the test statistic t) duoc tmh theo cong thurc:
t = (*, - X2) - ( / / , - M2)
Lu$n van tot nghiep Do Thi Bich Loan
j 2f i o
— + —
v wi 2 / 2 _ (K, -1 )sf +(n2 - 1 > 22
/?, +ô2 - 2
s, =.
n, - 1
S 2
n2 -1 Trong do:
F , , .F, la so binh quan cua to 1 va to 2,
H,, / / , la ky vong toan cua tat ca cac don vj cua tong the chung vdi cac luong bien nhu cua to 1 va to 2,
n, va n2 la so don vj cua to 1 va to 2,
s, va s2 la do lech tieu chuan cua td 1 va to 2.
L u£n vMn tc ft nghiep — jsS — T)6 T h i B ic h L o o n
Kidm dinh thuc hien nhu sau:
H(): (//, - M i ) = 0 H , : (//, - / / 2) * 0
Bac bo H„ n e u |/| > ' 0,,,„, + „2- 2 Vi;ằ,+ằ.2 - 2 du(?c tra trong biing l-
Phuong phap phan to giup ta xac djnh duoc xu hudng thay ddi cac tieu thu’c ket qua do tieu thuc nguyen nhan gay ra chu khong luong hoa duoc muc do anh huong cua tung tieu thu’c nguyen nhan den su bien dong cua tieu thuc ket qua. Chang han, khi chu trang trai co trinh do hoc van tang them mot nam hoc tap thi gia trj san gia tang cua trang trai tang them bao nhieu dong hay khi chu trang trai hoc qua ldp quan ly kinh te trang trai thi gia tri gia tang se tang len bao nhieu so voi khi chua duoc hoc cac ldp tap huan nay?
Ben canh dd, phuong phap phan to khong true tiep dua ra (muon cd, ta phai tu tmh toan) cac thong tin de kiem dinh duoc do tin cay thong ke ve su khac nhau ve gia tri cua tieu thu’c ket qua giua cac td, tuc la kiem dinh do tin cay thong ke ve anh hudng cua tung tieu thuc nguyen nhan den su bien dong cua tieu thurc ket qua.
Ham hoi quy cd the giup khac phuc duoc cac nhuoc diem tren day cua phuong phap phan to. Do vay, trong khi nghien curu kinh te ngudi ta dung pho bien cac ham hoi quy, dac biet la ham san xuat dang Cobb- Douglas de nghien cuu su anh hudng cua nhung tieu thu'c nguyen nhan den tieu thuc ket qua.
- Ham san xuat Cobb - Douglas (ham CD) Khai niem ham san xuat:
"Ham san xuat la ham bieu di£n su phu thuoc cua ket qua san xuat kinh doanh ddi vdi cac yeu td chi phi bo ra trong qua trinh san xuat".
Ham san xuat cd dang:
Y = f(x „ x 2...xi,...x„ D„ D 2...Dj...Dm);
Trong do: Y la yeu td ket qua san xuat (Bien phu thuoc).
x, La cac yeu to nguyen nhan, hay mire dau tir cac yeu to san xuat dau vao (Bi£n doc lap).
Dj la cac bien gia dinh, D, thudng nhan cac gia trj la 0 hoac l(va cung la bien doc lap).
Ham san xuat Cobb-Douglas cd dang:
Y = a * x x , al. . . *x„a". e h'DI ...eh2D]... ehmDm(\) Trong dd Y, x , , Dj da duoc djnh nghTa d tren.
Ham san xuat Cobb - Douglas duoc goi theo ten cua nha kinh te P.H.Douglas va nha thong ke C.W.Cobb trong cong trinh nghien cuu ve kinh te My tu 1899 den 1922. Hai ong da tim ra ham sd san xuat cua nen kinh te My trong giai doan dd la:
Q = K*’ 75 L025 Trong dd:
K: Von ky thuat.
L: Lao dong
Ham sau xuat CD co nhtfng iCu diem sau:
- Phu hop vdi ly thuyet kinh te ve quy luat dau tu tham canh.
- Tmh toan don gian vi cd the ehuyen ve dang tuyen tmh don bang cach Logarit hoa hai ve cua (1) nhu sau:
LnY = lna() + a,Lnx, + a2Lnx2 ... + altLnxn + b,D,+ b2D 2-\- ...+bJDm Bai toan CD cd the duoc giai nhd ung dung phan men EXCEL nhanh va chmh xac.
Su dung bai toan CD, de bo tro cho phuong phap phan to, vi bai toan CD vira cd the tim ra xu hudng tac dong cua cac yeu td dau tu san xuat va luong hoa duoc sir tac dong dd, han nua bai toan CD kiem djnh dugc do tin cay cua cac dai lugng thong ke trong bai toan thong qua cac he thong chi sd do bai toan cung cap.
Phan tich ket qua bai toan:
M ultiple R: He sd tuong quan boi cho thay trinh do chat che cua mdi lien he tuong quan boi (0< R < /) ,
Lu£n van tot nghiep — _____ Th[ Bich Loan
R Square (R2) He so xac dinh: Cho biet bao nhieu phan tram sir bien dong cua bien phu thuoc duoc giai thfch boi cac bien doc lap da duoc bao g6m trong loai hinh.
O bservation: Sd don vi mSu duoc dua vao nghien curu.
F - stat: Tieu chuan F dung lam can cur de kiem djnh do tin cay ve mat khoa hoc (Thong ke) cua toan bo phuong trinh hdi quy. Bai toan du y nghla thong ke khi F > Fu.
Regression Coefficients (a, hoac bj): Cac he sd hoi quy a, ( i= l, 2,.. n ) noi len % thay doi cua Y khi X; tang them 1%, khi gia thiet cac yeu td khac khong doi, Do chfnh la do co dan cua san luong theo yeu td san xuat co he sd hoi quy a ;. Cac he sd hoi quy bj( j = 1,2 ..., m) noi len anh hudng cu the cua cac bien thuoc tmh khi no thuc sir say ra tren thuc te.
T - stat: Tieu chuan T dung lam can cu de kiem dinh do tin cay ve mat khoa hoc (thong ke) cua do co dan a; (i = 1 ,2 ,.. .n) tuc la mdi lien he giua Xj va Y.
P - Value: Xac suat de t > t-stat, dung de kiem djnh do tin cay ve mat khoa hoc (thong ke) cua do co dan a; (i = 1, 2, ... n) cua Y theo X j, hoac cua he s o h o i q u y b j (j = l,2 ,...m )
(1- P value) la do tin cay ve mat khoa hoc (thong ke) cua viec udc luong do co dan bieu hien mdi lien he cua Y theo Xj
Quy trinh udc luang ham san xuat CD bang phan mem EXCEL Budc l: N h a p so lie u Y, X,...Xi...Xn
Budc 2: Tmh LnY, LnX,..., L n X ;..., LnXn
Budc 3: Chon Tools tren thanh Menu cua Worksheet
Budc 4: Chon Regression sau dd chon OK, hop thoai Regression se xuat hien
Budc 5: Trong hop thoai Regression:
- Chon Input Range:
Input Y Range: khai bao vung d u lieu cho bien phu thuocY Input X Range: khai bao vung du lieu cho cac bien doc lap X
LuJin van ttft nghi&j? — 06 Th[ Bich Loan
Lu$n v2n t ot nghiep — Do ThiBich Loan
- Chon Output Options:
Output Range: khai bao vung ket qua xuat hien Cuoi cung bam OK.
- Phuong phap hach toan kinh te: Day la cong viec khong the thieu ddi vdi M't ky mot trang trai nao, qua hach toan kinh te se cho thay duoc trang trai do san xua't co dem lai hieu qua khong tu do giup trang trai xay dung duoc ke hoach san xuat trong thdi gian tdi. Phuong phap duoc sir dung de tmh toan chi phi san xuat va ket qua san xuat tu do se tmh duoc gia trj gia tang cua trang trai trong thdi gian mot nam.