Kien thuc tong hop kinh tế lượng

7/28/2019 Kien thuc tong hop kinh t lng

1/23

Nm 20101

N TP KINH T LNG1. Phng php c lng bnh phng cc tiu LS,l chn cc tham s c lng

Kkk ,..,2,1,^

sao cho lm cc i ph hp 2R . Hn na, iu i hi iu

kin rng : 2)(

yyTSS nn l bt bin vi mi s la chn tham s c lng.

ng Sai

Gii thch:

TSS

ESSR 12 , phng php LS l chn Kkk ,..,2,1,

^

sao cho cc tiu ESS. V

TSS khng i vi mi la chn. Nn Cc tiu ESS ng ngha vi cc i 2R .

2. Nhc li l hi quy LS c th c vit di dng sau: Kkc nnkkk ,..,2,1, .Vic chng minh c lng ny l khng chch: KkE kk ..,2,1, , i hi githuyt rng n c phn b chun.

ng Sai Gii thch:

)( nnkkk cEE . V vy, ch cn iu kin: ,0nE vi mi n l .

3. Nhc li rng, kkk SVar2^

)(

. Trong , kkS l phng sai mu ca bin kX . iuny hm rng, vic ly mu t tng th cng a dng, th hiu qu c lng cngtng. Hay cng vy, vic ly mu cng tng t nhau, th chnh xc ca clng cng gim.

ng Sai Gii thch:

Vkk

kS

Var2^

)(

, nn khi kkS tng th sai s c lng gim, hay hiu qu c lng tng

4.Nhc li, ),(~ 2kk

kkS

N

. Kt lun ny ch i hi s dng gi thuyt ),0(~ 2 Nn ,

m khng cn thm bt c mt gi thuyt no khc v sai s ngu nhin.ng Sai Gii thch:

Chng minh iu ny yu cu rng, ),0(~ 2 Niid

n , hay cc sai s ngu nhin phi c lp.

5. c lng khng chch ca 2 l

22 1ne

KN

s . N c s dng bin i

phn b chun kz thnh phn b t-student vi (N-K) bc t do: )(~ KNttk .

ng Sai


2/23

Nm 20102

Gii thch:

V rng )2(~)(

^

^

2

Nt

seSst

XX

6. Hy xt vic kim nh gi thuyt sau: 0:0 kH .vs. 0:1 kH . Nu p-valuenh hn 5%, th ta ni

k c ngha 5%.

ng Sai 7.Nu tt c cc quan st },{ 'nn xy c th c biu din thnh mt m my d liu,

nm gn trong khng gian hai chiu (dng th phng, vi hai trc), th vic tngs bin gii thch ln hn 2 bin s khng lm gim 2R . Nhng nu chui cc quanst },{ 'nn xy cn phi biu din trong khng gian 3 chiu ( th 3 trc), th vic tngs bin gii thch ln hn 2 bin s thc s lm tng 2R .

ng Sai

Gii thch:y l nguyn tc ca LS.

8.Nhc li l)1/(

)/(1

2

NTSS

KNESSR . Khi a thm bin vo m s ci thin v ph

hp t hn so vi s mt mt t do, th

22 1ne

KNs tng, v

2

R cng tng.

ng Sai Gii thch:

T cng thc, ta thy 22

1ne

KNs phi gim, v do vy nn

2

R mi tng.

Hai cu tip sau lv s la chn v m hnh:(U): 332211 XXXY

(R):~

11 XY

Sai lm loi I l m hnh (U) ng, nhng li c lng bng m hnh (R).Sai lm loi II l ngc li, m hnh (R) ng, nhng li hi quy m hnh (U).

M hnh (R) Chng qua chnh l m hnh (U) vi rng buc: 0: 320 H .

Nu ta khng th bc b gi thuyt ny ( 0DNRH ), m vn hi quy m hnh (U), th s cithin v ph hp so vi (R) s rt t, trong khi mt mt v bc t do s cao. Hay 2s s c xu hng tng. Da vo nhn nh , hy tr li cu hi sau:

9. S dng hai tnh cht thng k ca c lng LS: (1). )()( ^ nnkkk cEE ; v(2). nh gi sai s c lng l

kk

k

S

sVar

2^

)( . Khi , ta c th i n nhn nh

rng a thm bin gii thch khng cn thit vo m hnh s vn cho ra c lngkhng chch. Nhng chnh xc ca c lng gim i.


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Nm 20103

ng Sai

Gii thch:

)()(^

nnkkk cEE = k , do gi thuyt v sai s ngu nhin khng b vi phm. Tuy

nhin, v 22 1neKNs tng, nn kk

kS

s

Var

2^

)( cng tng, hay chnh xc gim.

10.Gi s m hnh (U) l ng, nhng chng ta li hi quy theo m hnh (R). Khi ,cc bin c ngha, nhng b b qun khng a vo m hnh s b cng dn li

sai s ngu nhin. Tc l: 3322~

XX

Da trn nhn xt , ta c th nhn nh rng, vic b qun cc bin c ngha s lmcho c lng b chch, v mi kim nh thng k tr nn v ngha.

ng Sai

Gii thch:

V 03322~

XX , nn c lng b chch. Do khng th lp t-test.

11.Gi thit 0)|( ' nn xE , tng ng vi vic ni rng, '' )|( nnn xxyE .Tr li: Cu ny ng, v rng:

,)|( ''' nnnnnn xxyExy nu 0)|('

nn xE .

12.Gi thit cc vc t quan st th ': nxn khng phi ngu nhin bao hm KrankX .Tr li: Cu ny sai, v y l hai gi thit khc nhau.

13.Gi thit ),0(~ 2IN bao hm rng, 0),cov( mn , vi mn .Tr li: cu ny ng, v IVar 2 , tc l 0),cov( mn , vi mn .

14.Gi thit KrankX l bo m cho tn ti c lng .Tr li: Cu ny ng. i hi KrankX bo m s tn ti ca ma trn 1)'( XX , m

l iu kin tnh c YXXX ')'( 1^

.

Xut pht t cng thc 15.Gi thit IE 2)'( , bao hm rng, 0),cov( mn , vi mn .

Tr li: Cu ny ng.


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Nm 20104

Chng minh hoc l gii cc mnh sau:Di dng tng qut, c lng c vit nh sau:

YXXX ')'( 1^

M hnh hi quy c dng: Xy , X khng phi l bin ngu nhin; v ),0(~ 2IN .

16.Ch ra rng, trong kim nh vi F-test, nu gi thit 0H l ng, th F-stat nhn gitr nh hn khi 0H l sai.

Tr li:)/(

/)(

KNESS

JESSESSF

U

UR

. Nu 0H l ng, th vic thm bin gii thch khng lm

ci thin nhiu ph hp ca m hnh. Tc l UR ESSESS nhn gi tr nh; v vy F-value nhn gi tr nh.

17.Ch ra rng, vi c t-test v F-test, nu 0Hb bc b th p value s nh hn mc c ngha %.

Tr li: p-value nh chng t thng k F (hoc thng k t) nm bn phi ca F hoc

2/t . Do vy, cn phi bc b 0H .18.Ch ra rng, F- stat bao gi cng nhn gi tr dng.

Tr li: RESS bao gi cng ln hn UESS .

19.Thng k )1,0(~/2

^

NSz kk

kk

k

c rt ra t gi thit l )/,(~2

^

kkkk SN .

Tr li: Cu ny ng.

20.Thng kkk

kkk

Sz

/2

^

l mt dng vit khc ca kt -stat.

Tr li: Cu ny sai. Vkk

kkk

Sst

/2

^

21.M hnh kinh t lng c th vit di dng: XXXXY KK....2211

Tr li:Cu ny ng

22.Gii thch xem vic a p value vo bng kt sut c g khc vi bo co v gi trca t-stat hoc F-stat.

Tr li: P-value cho bit gi tr cu F-stat (hoc t-stat) nm bn phi hay tri ca im tihn F (hoc 2/t ). Do vy, cn phi bc b hay chp nhn 0H .

23.Ch ra l t-stat c th nhn gi tr m hoc dng.


5/23

Nm 20105

Tr li:kk

kkk

Sst

2

^

; v c lng k

^

c th nm bn tri hoc bn phi gi tr thc ca

tng th k .

24.t-stat dng kim nh tnh c ngha ca phng trnh hi quy (overallsignificance test)

Tr li: Cu ny sai. F-test mi c th c dng kim nh ngha ca phng trnhhi quy.

25.Khi a thm bin khng cn thit vo m hnh, standard error (se) ca cc tham sc xu hng nh i.

Tr li: Cu ny sai. V lm nh vt s gim chnh xc ca c lng. Do vy, se c

xu hng tng.

26. IE 2' bao hm rng, 0),cov( mn , vi mn .Tr li: cu ny ng, v lch khi ng cho ca ma trn varian-covarian chnh l

0),cov( mn .

27.Khi kim nh gi thit n: 0:0 kH Liu t-test v F-test c th a ra cc kt lun khc nhau khng? Ch ra ti sao.

Tr li: Khi kim nh gi thit n: 0:0 kH , F-test v t-test l hon ton nh nhau v

ngha v kt lun, mc d l s dng 2 thng k khc nhau.

28.Gii thch xem vic a p value vo bng kt sut c g khc vi bo co v gi trca t-stat hoc F-stat.

Tr li: P-value cho bit gi tr cu F-stat (hoc t-stat) nm bn phi hay tri ca im tihn F (hoc 2/t ). Do vy, cn phi bc b hay chp nhn 0H .

29.F-test l tng qut hn so vi t-test.Tr li: cu ny ng, v F-test c th kim nh gi thit kp, trong khi t-test ch c thkim nh gi thit n.

30.Hi quy a bin c th vit di nhiu dng. Hy xt n 3 biu din sau:(i) Nnxy nnn ,..,2,1

'

(ii) Nnxy nn ,..,2,1^

'^

(iii) nnn yye

C (i), (ii), (iii) l ng


6/23

Nm 20106

31.Hi quy a bin bao hm vic gii bi ton sau:^min)()(

2^

'2^

n nnn xyeS

Hy xt mnh sau:

(i) H s Kkk ,..,2,1,^

c xc nh bng cch ly o hm ring phn, v t:

0)

(^

k

S

.

(ii) Ch cn tm KkS

k

,...,2,1,)(

^

, v t chng bng nhau xc nh Kkk ,..,2,1,^

.

Ch c (i) l ng

32.Gi s phng trnh hi quy c cha bin constant: 11 X . Xt cc mnh sau:(i) Vic gii: 0)

(

1

^

Sdn n ci iu l

0

n

e .

(ii) iu kin 0ne bao hm ci iu l^

'

xy , hay ng hi quy i quan im

trung bnh: ),( '

xy .

C hai mnh (i) v (ii) u ng33.Hy xt cc mnh sau:

(i) nnn eyy ^

(ii) nnn eyyyy ^

)( .

Hai mnh ny l tng ng nhau

34.Gi s ng hi quy i qua im trung bnh: ^' xy . Hy xt cc mnh sau:(i) nnn eyyyy

^

)(

(ii) nnn exxyy ^'' )()(

Mnh (ii) l c suy ra t mnh (i), s dng iu kin l ng hiquy i qua im trung bnh.

35.Xt quan h sau: 22^2 )()( nnnnnn eyyyy .(i) Quan h ny c ngha l: TSS = RSS + ESS(ii) Quan h ny c s dng xc nh h s 2R

C hai mnh u ng

36.Phng phpLScho ta c lng: Kkc nnkkk ,..,2,1, .Hy xt cc mnh sau:


7/23

Nm 20107

(i) c lng k^

l mt i lng ngu nhin

(ii) Nu khng c tc ng ngu nhin, th vic hi quy tr thnh tm thng, v ta lunc:

kk .

C hai mnh (i) v (ii) u ng

37.Hy xt tnh khng chch ca c lngLS:

)(nnkkk

cEE k

iu ny ng khi NnE n ,..,2,1,0

38.Hy xt quan h sau: )( ^ kkk VarVar iu ny ng, khi

kkE

39.Trong chng minh tnh cht sau: )( ^ kkk VarVar KkSkk

,..,2,1,2

.

Ta cn iu kin Nnn ,..,2,1, l cc bin ngu nhin c lp, v2 nVar

40. i n kt lun l ),(~ 2kk

kkS

N , ta c th phi cn nhng yu cu sau:

(i)kkE

(ii)kk

kS

Var2^

)(

(iii) Cc bin ngu nhin Nnn ,..,2,1, l theo phn b chun.

Cn c (i), (ii), v (iii)

41.Kim nh t-stat c dng sau: )(~)(

^

^

2KNt

seSst

k

kk

kk

kk

k

. xy dng thng

k ny, ta c th cn cc iu kin sau:

(i) ),(~2

kk

kkS

N

(ii)

n ne

KNs 22

1l c lng khng chch ca 2

(iii) Cc bin },...,,...,,{ 21 Kk XXXX l c lp tuyn tnh.

Chng ta cn iu kin (i) v (ii)42. Gi s ta a thm bin gii thch vo m hnh.

Tng bnh phng cc sai s c lng (ESS) lun gim xung

43.Hy nhn vo cng thc xc nh)1/(

)/(1

2

NTSS

KNESSR .

H s2

R v 2s lun bin ng nghch chiu nhauNu tng h s ring bit khng c ngha, nhng mt cch ng thi 43 , c

ngha, th ta nn gi 43 ,XX trong m hnh44.Xt hai m hnh:


8/23

Nm 20108

(U): KKXXXY ....33221

(R): JKJK XXXY ....33221

c hiu l: M hnh (R) l m hnh (U), cng vi rng buc0...: 210 KJKJKH

45.Xt 0...: 210

KJKJKH . Xy dng thng k )/(

)(

KNESS

JESSESS

F U

UR

c

.

Khi gi tr thng k cF ln hn F -tra bng, th ta nimt cch ng thi, ccbin KJKJK XXX ,..,, 21 l c ngha

46.Khi kim nh tnh c ngha ng thi ca tt c cc bin gii thch (overallsignificance test), ta s dng:

Thng k ),1(~)/()1(

)1(

2

2

KNKFKNR

KRFc

47.Xt hai nhn nh:(i) Vic khng loi b bin khng c ngha ra khi m hnh s vn cho c lng

khng chch theoLS, nhng vi chnh xc ti i.(ii) Vic b qun, khng a bin c ngha vo m hnh s lm c lng b chch.Trong cc mnh sau, u lmnh ng?

C (i) v (ii) u ng

48.Gis m hnh hi quy c dng )1(,..,2,1,33221 Ttxxy tttt . Gi s rngtrong m hnh (1), ta bit r rng 12 . Vic c lng tt nht (LS), khng chchca cc tham s 31 , s c thc hin nh sau:

Lp m hnh: tttt xxy 3312 v c lng bng eviews.

49.Xt chui cc quan st (m my d liu) sau:ty

x x x x x x x.x x x x x..xxxxxxxxxxxx

tx

Vic c lng m hnh: )2(,..,2,1, Ttxy ttt s cho thy:

M hnh ny c 12 R ch khng khng nh c l tt nht.50.Xt 2 chui cc quan st (2 m my d liu) sau:


9/23

Nm 20109

ty xx tz xxxxx

x xxxxxxxx xxxx

x x xxxxx xxxxxxxx

x x xxxxxx

x x x

tx tw

Vic c lng m hnh: )1.2(ttt xy v m hnh )2.2(ttt wz s chothy:

Ta nhn thy rng: )()( tt VarVar

51.Gis m hnh hi quy c dng )3(,..,2,1,....221 Ttxxy ttKKtt .Gi s rng trong m hnh (3), ta bit r rng 01 . Vic c lng tt nht (LS),s cho thy rng:

2R c th nm ngoi khong [0,1] do gp phi trng hp a cng tuyn.

52.Gis m hnh hi quy c dng )3(,..,2,1,....221 Ttxxy ttKKtt . Gi srng trong m hnh (3), ta bit r rng 01 . Vic c lng tt nht (LS), s chothy rng:

im trung bnh: ),( '

xy nm trn ng hi quy.

53.c lng LS cho ra kt lun rng, ),(~ 2kk

kkS

N

.

kkS tng th chnh xc ca c lng tng

tng th chnh xc ca c lng gim.

54.Gi s m hnh hi quy c dng )5(,..,2,1,33221 Ttxxy tttt . Gi s tabit r rng, khng c h ng thc Ttxaax tt ,..,2,1,3312 . Khi :

M hnh (5) cho ra c lng LS, khng chch, nu ),0(~ 2 Niid

t .

Do bit chc chn khng xy ra trng hp a cng tuyn.55.Xt hi quy bi vi K bin gii thch. c lng LS cho ra kt lun rng,

),(~2

kk

kkS

N

. V vy:

iu ny hm LS l c lng khng chch

56.Gis m hnh hi quy c dng )5(,..,2,1,33221 Ttxxy tttt . Gi s rngtrong m hnh (5), ta bit r rng Ttxaax tt ,..,2,1,3312 . Khi :


10/23

Nm 201010

M hnh ny khng th c lng cdo bit chc chn xy ra trng hp a cngtuyn.

57.c lng khng chch ca 2 l

22 1ne

KNs .

N c dng xc nh2

R hiu chnh.

N c dng xc nh phn b t-stat kt ca k^

58.Gi s ta bit r tt c cc quan st },{ 'nn xy c th c biu din thnh mt mmy d liu, nm gn trong khng gian ba chiu

Hi quy bi (K=3) cho c lng khng chchv ch ph thuc vo ng 3 bin.59.Gi s ta bit r tt c cc quan st },{ 'nn xy c th c biu din thnh mt m

my d liu, nm gn trong khng gian hai chiuVic dng hi quy n cho ra sai s ca c lng l nh nht ng vi hai bin.

60.Xt hai m hnh sau:

(U): 332211 XXXY

(R):~

11 XY

Ta chp nhn (R) nu vic thm 32 ,XX khng ci thin ph hp ca m hnh

Nu (U) ng, m dng (R) th c lng b chch61.INV l cu u t, c th ph thuc vo li sut (INT), lm pht (INF), hoc ch ph

thuc vo li sut thc (INT-INF). Ngoi ra n cn ph thuc vo xu th (T) vGDP (G). Xt hai m hnh khc nhau:

(8.1): INFINTGTINV 54321

(8.2): )(4321 INFINTGTINV

Ta chp nhn (8.1) nu F-test bc b 540 : H

62.Xt 3 dng hm: (10.1): XY 21 (10.2): XY lnln 21 (10.3): XY /21

Vi (10.2) n v o lng ca Y v X khng ng vai tr gv cng ph thuc vo %.

C ba m hnh trn u l m hnh hiquy tuyn tnh.

Si gn rt nhiu qun bia. V khng t sinh vin tm cch d on nhu cu ungbia ca dn Si gn. iu ny cng tng xy ra cc trng ca M.T l thuyt v tiu dng trong Kinh t Vi m, chng ta bit rng, nhu cu ung bia(Q , o bng lt) ph thuc vo gi ca hng ho BP , vo gi cc hng c th thayth ( LP ), c th l ru (liquor); v gi trung bnh ca cc hng ho dch v gii trkhc ( RP ); v vo thu nhp bng tin mt (m ). (Gi v thu nhp o bng $; v y

ta khng ni n mt thng hiu no c th, nn yu t qung co, brand name,vn vn, c b qua).


11/23

Nm 201011

S dng s liu iu tra ngu nhin trong sut 30 nm, t mt gia nh ngi M,chng ta mun nghin cu quan h ni trn, nhm nh gi li l thuyt tiu dngtrong vi m.

Dng hm hi quy ca m hnh c la chn nh sau:

M hnh (U): )ln()ln()ln()ln()ln( 54321 mPPPQ RLB 63. co dn ca nhu cu v bia theo gi c v thu nhp. V d, vi gi bia:

)ln(/)ln(2 BPdQd ; v vi thu nhp: )ln(/)ln(5 mdQd .

H s 2 th hin nhu cu tiu th bia gim bao nhiu % khi gi bia tng 1%, trong khicc yu t khc khng i.Tng )( 25 th hin nhu cu tiu th bia tng bao nhiu % khi gi bia gim 1%, v thunhp tng 1%, trong khi cc yu t cn li khng thay i.

Cc cu tip theo s dng kt qu c lng ca m hnh (U) l nh sau:

Dependent Variable: LOG(Q)

Method: Least Squares

Date: 08/02/01 Time: 01:01Sample: 1 30

Included observations: 30

Variable Coefficient

Std.

Error t-Statistic Prob.

C -3.243238 3.743000 -0.866481 0.3945

LOG(PB) -1.020419 0.239042 -4.268787 0.0002

LOG(PL) -0.582934 0.560150 -1.040674 0.3080

LOG(PR) 0.209545 0.079693 2.629415 0.0144

LOG(M) 0.922864 0.415514 2.221016 0.0356

R-squared 0.825389

Mean dependent

var 4.018531Adjusted R-

squared 0.797451 S.D. dependent var 0.133258

S.E. of regression 0.059973

Akaike info

criterion -2.638823

Sum squared resid 0.089920 Schwarz criterion -2.405290

Log likelihood 44.58235 F-statistic 29.54377Durbin-Watson

stat 2.630645 Prob(F-statistic) 0.000000

64.Thu nhp l yu t quan trng nh ng ti tiu dng. Tuy nhin, mi ngi c tht cu hi v h s c lng i km vi yu t thu nhp l kh ln v mc . Cth l 92.05

^


12/23

Nm 201012

c lng 92.05^

t ra vn . V kh m hnh dung rng, nu thu nhp tng 10%,th nhu cu v tiu th bia gn cng tng ln gn 10%. V vy, cn phi c nhng nhgi thng k b tr xt xem kt qu c lng l c hp l trn thc t khng. C

th l nn tm khong tin cy ca 5 .

65.Cc dch v gii tr khc, cng nh ru l cc loi hng thay th (substitution), haycnh tranh vi sn phm bia. V vy:Ch ring du ca gi ru ( 582.03

^

) l khng ph hp vi l lun v tiu dng; vru l hng thay th chonhu cu ung bia. Nhng iu ny vn c th chp nhnc, nu th trng cho thy, gi ru tng, th gi bia cng tng theo.

66.Ngi ta mun kim tra li, c thc s rng c thu nhp tng ln 10%, th mc tiuth bia cng tng ln ti gn 10% hay khng.V vy, ngi ta mun tnh khong tin

cy 95% ca h s 5 i km vi thu nhp, m, trong m hnh gc (U). Bit rng,06.2)25(025.0 t .

Khong tin cy 95% ca ]780.1;066.0[5 . Tc l co dn (elasticity) ca tiu thbia so vi thu nhp l c th nh hn rt nhiu hoc ln hn rt nhiu so vi gi trc lng. V vy, kt qu c lng l chp nhn c.

67.Chng ta cng nhn thy rng, h s i km vi gi ru 5829.03^ l khng phhp vi l lun v hnh vi tiu dng, do bia v ru l hai hng ho thay th nhau.

Tc l nu gi ru tng th ngi tiu dng nn tiu th bia nhiu hn thay choru. V vy, 3

^

ng ra phi c du dng, hn l du m. Hn na, h s clng ny li t c ngha ( p-value= 0.308). iu ny ch c th xy ra, nu gi thtrng ca ru tng, th ngi tiu dng cng on ngay l gi bia cng s tng;v do vy h s gim nhu cu v bia. Ni khc i thng tin v bin ng gi ca hailoi hng l c tng quan ng bin cht vi nhau. Trong kinh t lng, ngi tagi hin tng ny l a cng tuyn (Linear collinearity). kim tra nghi vn c ng hay khng, ngi ta chy hi quy b tr (auxilliary regression) sau, giagi ru v bia:

Dependent Variable: LOG(PB)

Method: Least Squares

Date: 06/10/09 Time: 15:36

Sample: 1 30


Variable Coefficient Std. Error t-Statistic Prob.

C -3.721925 0.240880 -15.45134 0.0000LOG(PL) 2.275450 0.113508 20.04664 0.0000


13/23

Nm 201013

R-squared 0.934864 Mean dependent var 1.102373Adjusted R-


S.E. of regression 0.057223 Akaike info criterion -2.819367

Sum squared resid 0.091687 Schwarz criterion -2.725954

Log likelihood 44.29050 F-statistic 401.8677

Durbin-Watsonstat 1.317876 Prob(F-statistic) 0.000000

T kt qu c lng b tr trn (auxiliary regression), ta c th ni rng:

H s 934.02 R th hin s tng quan cht gia vic thay i gi ca hai mthng bia v ru. V vy, c hin tng a cng tuyn.

68.V y l nghin cu hnh vi tiu dng ca h gia nh qua nhiu nm, m lm phtc th c nh hng. Hc thuyt tin t cho rng, nu gi c v thu nhp tng cngmt nhp, th s khng lm thay i nhu cu tiu dng hng ho. kim nh githuyt , t m hnh gc (U), ta c th vit li di dng sau:

)ln()ln()ln()ln()ln( 54321 mPPPQ RLB (15.1)

Trong , th hin nhp tng gi v thu nhp theo cng mt mc . Khai trin dnghm m t ny, ta c:

ln)()ln()ln()ln()ln()ln( 543254321 mPPPQ RLB (15.2)

So snh m hnh (U) v (15.2), vic kim nh hc thuyt tin t c ng hay khng, dnn ci iu l trong m hnh (U) ta a vo gi thuyt sau:

0)(: 54320 H , hay cng vy, 5324 . Nu ta khng bc b c githuyt ny, th m hnh (15.1), (15.2) v (U) l hon ton trng nhau, bt k l baonhiu. Tc l hc thuyt tin t l ng.

By gi, kim nh gi thuyt 0)(: 54320 H , hy th rng buc vo(15.2), ta i n m hnh sau:

(R): )]ln()[ln()]ln()[ln()]ln()[ln()ln(5321 RRLRB

PmPPPPQ

Hay cng vy,(R) )/ln()/ln()/ln()ln( 5321 RRLRB PmPPPPQ

y chnh l m hnh ban u (U), cng vi gi thuyt 0)(: 54320 H . Nikhc i, (R) l m hnh b rng buc ca m hnh (U), khi chp nhn ch thuyt tin t lng. Ch thuyt ny ni rng, nhu cu tiu th hng ho ph thuc vo gi tng ica hng ho so vi ch s gi sinh hot khc ,/ RB PP v thu nhp thc t ,/ RPm (ta cth xem RP nh ch s gi tiu dng). Kt qu chy m hnh ny l nh sau:

Dependent Variable: LOG(Q)


14/23

Nm 201014

Method: Least SquaresDate: 08/02/01 Time: 02:19

Sample: 1 30



C -4.797798 3.713905 -1.291847 0.2078

LOG(PB/PR) -1.299386 0.165738 -7.840022 0.0000

LOG(PL/PR) 0.186816 0.284383 0.656916 0.5170

LOG(M/PR) 0.945829 0.427047 2.214813 0.0357

R-squared 0.807949 Mean dependent var 4.018531

Adjusted R-


S.E. of regression 0.061676 Akaike info criterion

-

2.610291

Sum squared resid 0.098901 Schwarz criterion

-

2.423465

Log likelihood 43.15437 F-statistic 36.46021

Durbin-Watson

stat 2.686998 Prob(F-statistic) 0.000000

Ch l trong bng kt xut cho m hnh (U) cu 11, 08992.0UESS ; v bng ktxut ny cho m hnh (R), 09890.0RESS . Thm vo , 24.4)25,1(05.0 F . Hy kim nhli gi thuyt 0H va nu ca ch thuyt tin t, v hy kt lun xem:

Nhu cu tiu dng ch ph thuc vo gi tng i ca hng ho (so vi ch s gitiu dng, hay lm pht), v mc thu nhp thc t.

Sc hp dn ca rp Galaxy l ti b cun ht bi nhm cc bn K05402 gmNgc Bo (trng nhm), Phng Dung, Quc Hnh, ng Khoa v Phm Tng.Vn l nhng ngi yu thch xem phim, ng thi, cng thy l mt th vui khc bit ca ngi dn Si Gn, cc bn tm hiu cc yu t tc ng ti s ln

mt ngi n xem rp Galaxy trong mt thng. S d l Galaxy, m khng phirp khc, l do s khc bit ca n trong vic hnh thnh mt t hp gii tr phchp, sang trng, cnh quan p, phong cch phc v chuyn nghip, c c bar-caf,shop vn ha phm, beauty salon, v.v...

B nh hng bi quan im ca trng phi Societal Marketing, c khixng bi Phillip Kotler, cc bn phn loi cc yu t nh hng ti hnh vi canhng ngi n rp Galaxy nh sau:

Nhm bin iu kin c nhn, bao gm:

AGE ( tui), k vng l mang du m: tr hn th hay i xem phim hn. INC (thu nhp, triu ng), k vng l mang du dng: giu hn th hay i

xem hn.


15/23

Nm 201015

DIST (khong cch t nh ti rp Galaxy, km), k vng l mang du m. FRIENDS (bin Dummy, rng c hay i vi bn hay thch i mt mnh)

Nhm bin tc ng ti tm l khch hng, bao gm:

PR (mc a thchs gim gi 50% vo ngy th 3, chia lm 3 cp , tngdn), k vng l mang du dng

SPACE (mc a thch s thong ng, sang trng ca Galaxy, chia lm 5cp , tng dn), k vng l mang du dng.

CINEMA (bin Dummy, rng Galaxy c phi l s la chn s 1 hay khng),k vng l mang du dng.

DVD (thch n rp hn l xem DVD ti nh, chia lm 3 cp tng dn), kvng l mang du dng.

Bin c gii thch l TIMES (s ln i xem Galaxy trong mt thng).Nhm iu tra 120 mu. Kt qu c lng nh sau:

FRIENDSDISTINCAGETIMES 02166.0005425.0002944.01087.0***

(0.023814) (0.013711) (0.031695) (0.088697)

+ ********** 245.53659.01504.0548.04369.0 DVDCINEMASPACEPR

(0.21) (0.1515) (0.2469) (0.1566) (1.16)

Ghi ch: S trong ngc l standard error.*** l c ngha mc 0.01; ** l c ngha mc 0.05; * l c ngha

mc 0.1

N=120, 898.02

R , AIC =2.363, SCHWARZ = 2.572, 264.64UESS .

69.Kim mh tnh c ngha mc 0.05 (hay 5%) ca tng bin sau: INC, DIST, vCINEMA, FRIENDS. Cho trc 626.2]120[05.0 t . Trong cc mnh sau, u lmnh ng?C 4 bin INC, DIST, CINEMA, v FRIENDS l khng c ngha

70.Gi s bin FRIENDS l khng c ngha. V bin CINEMA cng nn b i, vch c nhng ngi cc k m Galaxy th mi n y t tin. Nn nhm quytnh loi b 2 bin .

Tuy nhin, i vi cc bin INC, DIST, kh m c th ni chng khng tc ng nhnh vi ca ngi tiu dng. Theo l thuyt ca Keynes, v ni rng thu nhp (INC) lyu t chnh quyt nh ti hnh vi ngi tiu dng, nht l rp t tin nh Galaxy. Vvy, ta khng c php bc b Keynesv i, khi cha th nghim. Nhm bn quytnh tin hnh kim nh gi thuyt ng thi:

0:0 FRIENDSCINEMADISTINCH

M hnh c rng buc [tc l ng thi b i INC, DIST, CINEMA, v FRIENDS] c53.64RESS . Cho trc 4534.2)111,4(05.0 F . Nu l em, em s chn quyt nh no trong

hai quyt nh sau y?


16/23

Nm 201016

Chp nhn gi thuyt ( 0DNRH ), v quyt nh loi DIST, CINEMA, FRIENDS, v nhtl INC, ra khi m hnh.

71.Gi s cc bn quyt nh chp nhn gi thuyt, da trn kt qu r rng ca kimnh ca Wald test. Tc l loi b INC v cc bin va nu ra khi m hnh. Khi

bit iu , vic bc b Keynes v i l iu kh chp nhn c. C kh nngmt bin no c ngha, m li b B QUN, khng a vo m hnh, th slm c lng b chch. V mi kim nh thng k tr nn v gi tr. C th ccem cha a ht cc bin c ngha vo m hnh.

Nh vy tc ng ca thu nhp (INC), rt c th l khng theo dng tuyn tnh. Nh vydn n suy ngh: Hy a cm bin INCv 2INC vo m hnh. Kt qu c lng nhsau:


AGE - 0.092405 0.011728 - 7.878932 0.0000

INC 0.064029 0.018296 3.499539 0.0007

INC^2 - 0.001559 0.000421 - 3.703025 0.0003

PR 0.675378 0.137521 4.911103 0.0000

SPACE 0.481140 0.129654 3.710939 0.0003

DIST - 0.034271 0.013322 - 2.572565 0.0114

DVD 0.331046 0.107549 3.078110 0.0026

C 4.524806 0.605613 7.471443 0.0000

Weighted Statistics

R-squared 0.939754 Mean dependent var 3.164710

Adjusted R-squared

0.935988 S.D. dependent var 2.892316

S.E. of regression 0.572007 Akaike info criterion 1.785009

Sum squared resid 36.64550 Schwarz criterion 1.970842

Log likelihood -99.10056 F-statistic 249.5762

Durbin-Watson

stat1.632296 Prob(F-statistic) 0.000000

By gi hy xem cc mnh sau:(i) Ngi cng giu th s lt i xem (TIMES) cng nhiu, nhng vi nhp tng gimdn.


17/23

Nm 201017

(ii) H s 93.0_2

R , gn bng 1, chng t mc chnh xc ca d bo s rt tt. Gnnh mc tuyt i. Tc l s ln i theo nh d bo t m hnh s xp x vi quanst thc.

Ch c (i) ng72.Nh vy cho thy kt qu c lng by gi ph hp vi l thuyt Keynes. V m

hnh c lng l kh tt v cc h s nh gi.Nhm chy th d bo. Sau y lkt qu d bo cho mt s quan st u tin:

obs TIMES TIMESF

1 0.500000 0.070385

2 4.000000 4.121212

3 2.000000 1.963325

4 0.500000 0.212924

5 4.000000 4.288887

6 0.750000 0.899692

7 1.000000 0.8932568 1.000000 0.742271

9 10.00000 7.326865

10 1.000000 1.092601

Trong , TIMES l quan st thc; TIMESF l d bo t m hnh. Chng ta c th thyl dbo khng tt lm, nu s lt i rt t (obs = 1, 4), hoc rt nhiu (obs =9). Datrn nhn xt , gi s Ban ging hun cng nhm sa li m hnh mt ln na. Vkt qu d bo l nh sau:

obs TIMES TIMESF1 0.500000 0.665557

2 4.000000 4.003906

3 2.000000 1.935964

4 0.500000 0.666090

5 4.000000 4.013686

6 0.750000 1.094529

7 1.000000 1.034579

8 1.000000 0.936783

9 10.00000 9.596951

Da trn kinh nghim thc t ny, em hy suy ngh nghim tc v li khuyn sau:

(i) H s _2R cao chng c ngha g lm, v khng nn v th m sa s liu lm g.(ii) Hy trung thc trong nghin cu nh nhm ca Ngc Bo. Bn s thy c nim

vui ca s sng to v kh nng khm ph thc t ca chnh bn.By gi, em hy chn cho mnh cch ng x (y l cu hi iu tra, khng nht thitu l cu tr li ng nht).

(a) Ti khng quan tm!(b) Ti ng v s khuyn la n em i sau v iu (i) v (ii) nu trn.


18/23

Nm 201018

(c) Ti cho l Ban ging hun nn c kin nghim khc hn vi nhng trnghp sa d liu trong tng lai nhm thc y tnh trung thc trong cngvic v s cng bng. (Cho d l ch pht hin c sau khi bo co hontt).

Quan im ca sinh vin v quan h tnh dc trc hn nhnTrong vi thp nin gn y, rt nhiu nhng nghin cu ch ra rng, hin tnglin quan n tnh dc ca gii tr nh sng th, no thai, ang ngy cng phbin. V iu ng ni l cn st tnh yu cng nh hng ti gii sinh vin. chnh l ch nghin cu ca nhm cc bn K05405 gm Phng H (trngnhm), nh Hng, an Thanh, L Thy v Hi Yn.Da trn nhng nghin cu x hi hc v tm l hc, nhm ch ra cc nguynnhn lm tng mun c quan h tnh dc (QHTD) trong sinh vin, (k hiu l

ACTION ), l nh sau:

Quan im v tnh dc trc hn nhn (OPINION): rng l vic khng nnlm, bnh thng, hay coi y l cch sng th, (c chia theo 3 cp tng dn). Kvng mang du dng.

L do v kinh t (COST): nhiu ngi t n vi nhau chia s ph tn sng,tin thu nh tr (tnh theo triu ng). K vng mang du dng.

S quan tm ca gia nh (FAMILY): chia lm 3 cp , ty vo vic b m tquan tm, va phi, hay rt quan tm. Nu s quan tm qu mc, cng ngngha vi g b hn, th h s mang du dng, th hin s phn ng ngcvi quan im truyn thng. Ngc li, nu s quan tm to ra kh nng

kim ch cao hn th h s c th mang du m. Yu ng (LOVE): nhn gi tr 1, nu ang c ngi yu, v 0 nu khng c.

ang yu, th d xy ra quan h tnh dc hn. K vng mang du dng.

Gii tnh (GENDER): nhn gi tr 1, nu l nam gii; v 0 nu l n. V namc quan im thong hn nn ta k vng h s mang du dng.

Ni (ROOM): nhn gi tr 1, nu nh tr, v 0 nu gia nh hay k tcx. Mt iu tra 300 sinh vin ti H ni cho thy, quan h tnh dc a phnxy ra nh tr, ni cc bn sinh vin c hon ton t do sinh hot, khng

chu s kim sot ca bt c ai. V vy, ta k vng h s mang du dng. im hc tp (MARK): Nhng ai tp trung u t vo vic hc nhiu hn, th

ngi b chi phi bi quan h tnh dc hn. Do vy, k vng du l m. Thhin rng, kh nng h c quan htnh dc l t i.Nhm iu tra 110 mu quan st ti Th c.

Kt qu c lng l nh sau:FAMILYCOSTOPINIONACTION 331.0567.0313.1705.0 ***

(1.81) (0.384) (0.795) (0.406) ******** 593.01194.09964.0872.0 MARKROOMGENDERLOVE

(0.414) (0.420) (0.3793) (0.2267)


19/23

Nm 201019

Mc-Fadden 2R =0.34, AIC = 0.7449, Schwarz = 0.941

Ghi ch: H s trong ngoc l standard error. Mc_Fadden- 2R c ngha tng t

nh_

2R .

H s i vi du *** l c ngha mc 0.01, ** l mc 0.05, v * l mc

0.1.

73.Hy kim mh tnh c ngha mc 0.05 (hay 5%) ca tng bin sau: COST,FAMILY, v ROOM. Cho trc 626.2]110[05.0 t . Trong cc mnh sau, u lmnh ng?C 3 yu t, COST, FAMILY, v ROOM l khng c ngha

74.Gi s sau khi kim nh t-test, nhm nghin cu i n kt lun l c 3 yu t trnu phi b loi b. i vi yu t nh tr(ROOM), n c th khng c ngha

lm ti kh nng xy ra quan h, v nu cn th ai cng c th i thu.Nhng r rng l,ng trn phng din l thuyt v thc tin, ta thy rt kh chp nhnvic loi b tc ng ca gia nh (FAMILY), cng nh ph tn sng (COST), ra khinhng cn nhc thit hn trong u c nhn: rng nn c hay khng quan h vi bn tnh.Chnh v vy, nhm quyt nh tin hnh kim nh ng thi:

0:0 COSTFAMILYH

Gi s kt qu kim nh cho bit 565.0cF . Cho trc 09.3)110,2(05.0 F . Nu l em, ems chn quyt nh no trong hai quyt nh sau y?

Chp nhn gi thuyt ( 0DNRH ), v quyt nh loi COST v FAMILY ra khi m hnh75.Gi s da trn kt qu r rng ca kim nh ca Wald test, cc bn quyt nh

phi loi b cc yu t COST v FAMILY ra khi m hnh.

Gi s thm rng, sau khi bit iu , TS.Hong B Thnh, PG Trung tm Dn s vcng tc x hi, ngi t chc iu tra 300 sinh vin ti H ni v quan h tnh dc,cho rng, l iu kh c th chp nhn c. ng vin dn nhng nh kinh in, nhFreud, rng hnh vi ca c nhn v tnh yu v hn nhn chu nh hng mnh m bimi trng gia nh, v bi nhng cn nhc thit hn v kinh t.

Gi s tip l TS Thnh quen thy Nht. ng ta nhc nhm trng rng: Thy Nht ccho bi tp, nu ln rng, nu c mt bin no c ngha, m li b B QUN, khnga vo m hnh, th s lm c lng b chch. V mi kim nh thng k tr nn v gi tr. C th cc em cha a ht cc bin c ngha vo m hnh.

Nh vy, tc ng ca ph tn sng, COST, rt c th l khng theo dng tuyn tnh. Gi: Hy a cm bin COSTv 2COST vo m hnh.Kt qu c lng nh di y:

Variable Coefficient

Std.

Error t-Statistic Prob.


20/23

Nm 201020

OPINION 1.686085 0.458461 3.677704 0.0002

COST 27.88161 7.407080 3.764183 0.0002

COST^2 -13.31335 3.507603 -3.795569 0.0001

FAMILY 0.646435 0.334938 1.930010 0.0536

GENDER -1.654577 0.436106 -3.793979 0.0001LOVE 0.885306 0.358623 2.468625 0.0136

MARK -0.532661 0.243442 -2.188043 0.0287

C -13.30959 4.414981 -3.014643 0.0026

R rng l c COST v FAMILY u c ngha. By gi, em hy xem cc mnh sau:(i) Ph tnsng, nh thu nh tr (COST) cng cao, th cng lm quan h tnh dc d

xy ra hn, nhng vi p lc gim dn.(ii) Trong gii sinh vin, yu ng lm quan h tnh dc trc hn nhn d xy rahn.C (i) v (ii) u ng

76.Hy chn nhng quan im ng (khng nht thitch c MT mnh l ng,m c th nhiu hn):

p lc ca ph tn sng ti th vi gi thu nh t v nhu cu chi tiu ln hn,l yu t tc ng mnh nht ti vic c nhn sinh vin chn sng chung vi bn tnh.

Trong mi cp sinh vin, vic c hay khng QHTD trc hn nhn ch yu l cquyt nh (hay c s ng thun) bi phi n, ch khng phi b thc y bi munnng vi ca phi nam.

S quan tm nhiu hn ca gia nh khin cho sinh vin d c kh nng c quan htnh dc trc hn nhn hn. iu ny c th l do h thy c n hn khi xa gia nh.Hoc ngc li, h t tin hn v vic chn ng bn tnh, theo nh cch nhn nhn cangi ln trong gia nh ch bo.

Vic quan tm hn n hctp v s thnh t trong tng lai lm chm li munc quan h tnh dc hoc c gia nh ca gii tr.

Quyt nh kinh doanh ca sinh vin

Kinh doanh khng phi l iu g xa l. Nhng khng phi ai cng hiu r nhngyu t g thc y mt con ngi tr nn am m v thnh cng trong kinhdoanh...nht l khi h vn cn l sinh vin. i khi, nhng tng ln bin mtsinh vin tr thnh nh kinh doanh thnh t, nh Bill gate, Microsoft, hay nhngngi sng lp ra Yahoo, hay Google. Nhng trong a s trng hp, nhng thnhcng ln trong kinh doanh thng bt u bng nhng cng vic nh, v nhng tng to bo thng to nn s k diu.


21/23

Nm 201021

Phi chng vic nng tm kim nhng c hi, v kh nng dm ngh n nhng tng mi l, d l rt ri ro, l nhng yu t bn tr thnh ngi thnh ttrong kinh doanh? l ch cun ht s quan tm ca cc bn Nguyn vnChin, V Hnh, v quang Sang (K06404 -401). L nhng ngi theo hc thuytca Icek Ajzen (Theory of planned behaviour), tm dch l thuyt hnh vi chng ch, cc bn chia nhng nhn t nh hng ti quyt nh tham d vo

kinh doanh khi cn l sinh vin thnh 3 nhm ln sau:Th nht, yu t tm l thch hay ngi ri ro (k hiu l RISK), m n phn nhquan im, thi , s a thch hay ngi ngn hot ng kinh doanh, (c o tzero, l hon ton khng s ri ro, ti 100 l ht sc ngi mo him). K vngdu lm.

Th hai, yu t v mi trng, x hi, bao gm:EXTERNAL, l tng ha cc nh hng ca gia nh, bn b n quyt nh thamd kinh doanh ca sinh vin, ngay khi cn i hc. y l bin phn loi (Dummy).N nhn gi tr 1, nu c s gi , thc y, v bng zero, nu khng c. K vngmang du dng.TIME, l thi gian b vo c bo ch v kinh doanh, lm giu, vo tm kim ccmi quan h, c hi kinh doanh. n v o l gi/tun. K vng mang du dng.Th ba, l cc yu t kim sot hnh vi, m n bin tng, lng mong mun thnhhnh ng c th. Bao gm:POTENTIAL, n v o triu ng, l tng s tin ti a m c nhn sinh vin cth huy ng c lc cn thit. K vng mang du dng.FIELD: l bin phn loi, nhn gi tr 1, nu l sinh vin khi ngnh kinh t, v

zero, nu thuc cc ngnh hc khc. K vng mang du dng. (iu ny khnghn ng, nht l trong thi i dotcom).GENDER, cng l bin phn loi, nhn gi tr 1, nu l nam, v zero, nu l n, th xem cnh my ru c yng hng hn phi yu trn thng trng hay khng.K vng mang du dng.Cui cng, bin c gii thch l TRADE, nhn gi tr 1, nu c nhn sinh vinquyt nh lm kinh doanh (nh), v zero, nu khng.

Kt qu c lng l nh sau:*********** 1152.03375.0872.45769.1 TIMEEXTERNALRISKTRADE

(0.459) (0.7352) (0.2547) (0.05122)

GENDERFIELDPOTENTIAL 2041.04067.0017.0

(0.0107) (0.2632) (0.2539)

Prob( LR-stat) =0.0000, AIC = 0.745, Schwarz = 0.859

Ghi ch: H s c lng i vi du **** l c ngha mc 0.001, *** l mc 0.05,v * l mc 0.1. H s trong ngoc l standard error.


22/23

Nm 201022

77.Hy kim mh tnh c ngha mc 0.1 (hay 10%) ca tng bin sau:EXTERNAL, POTENTIAL, FIELD, v GENDER. Cho trc 65.105.0 Z . Trongcc mnh sau, u l mnh ng?Tt c cc bin ny u khng c ngha mc 10%

78.Gi s sau khi kim nh t-test, vi mc ngha 5% cho thy nn loi b binGENDER ra khi m hnh. (Nam n u l anh hng, mt khi dm vo thngtrng). Nhng kt qu cho thy, cc bin EXTERNAL, POTENTIAL, V FIELDvn khng c ngha mc 5%. Nhm nghin cu ngh rng, c th c lngkm chnh xc do a qu nhiu bin vo m hnh. V vy, khng nn loi b tt c,m ch mt vi bin trong nhm cc bin khng c ngha. t tin lm iu ,nhm tin hnh php th F-test v tnh c ngha ng thi ca cm bin ny.Kt qu kim nh cho thy:

)198,3(~6431.2 FFc . Hn na, 60.2)198,3(05.0 F . Vy ta i n kt lun l, mc ngha 5%, khng nn ng thi loi b tt c cc bin ny khi m hnh.

ng Sai

Gii thch:

025.0FFc . V vy nn bc b gi thuyt H-null.

79.Nhm i n nhn nh rng, bn b gia nh ng h, th c ngha l kh nng v tichnh huy ng c cng s di do. V vy, thay v vic a c cm binEXTERNAL, POTENTIAL, FIELD vo, nhm ch quan tm ti bin thc, l stin c kh nng huy ng khi cn thit, POTENTIAL. Kt qu c lng cho ranh sau:

************ 018.01148.0825.4916.1 POTENTIALTIMERISKTRADE

(0.399) (0.617) (0.049) (0.010)

Prob( LR-stat) =0.0000, AIC = 0.74, Schwarz = 0.80

Theo m hnh Probit, cng thc nh gi tc ng ring phn ca tng yu t ti khnng tham d kinh doanh ca sinh vin c xc nh nh sau:

k

kk

POTENTIALTIMERISKX

TRADEob

X

TRADEob ^)018.01148.0825.4916.1(

)1(Pr)1(Pr

Trong , k=2,3,4, tng ng ln lt vi POTENTIALTIMERISKXk ,, ; v l hm xcsut phn b chun.Da trn nhn nh , em i n kt lun l, kh nng sinh vin tham d vo kinh doanh

ph thuc mnh nht vo:


23/23

Kh nng chp nhn ri ro v n lc hc hi, tm kim c hi kinh doanh

80.Nu em vn a bin FIELD vo trong m hnh, th h s c lng i km s l0.42, vi mc ngha 10%. (Cc h s c lng khc vn gi nguyn du v mc ngha cho php). Trong hon cnh nh vy,

)017.012.059.1()1(Pr:0 POTENTIALTIMERISKTRADEobFIELD

)42.0017.012.059.1()1(Pr:1 POTENTIALTIMERISKTRADEobFIELD

Nh vy, vic c hc nhng trng v kinh t v qun tr kinh doanh s khin cho sinhvin d tham d vo hot ng kinh doanh hn so vi hc trng khc. Theo em cckt lun sau y, u l ci ng nht:

Nu thc tin cho thy hc sinh ngnh kinh t v qun tr kinh doanh thc s cham thch lm kinh doanh hn so vi cc ngnh khc, th tt nht l lm tng mc a dng ca quan st nng hiu qu c lng, m khng nn loi b binFIELD

Nn kim nh li cm bin FIELD v POTENTIAL xem c kh nng loi bng thi c hai bin ny khng? Nu khng th, th phi tng s lng quan st thu c kt qu c lng tt hn

Kien thuc tong hop kinh tế lượng

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