phep thu cho diem thi hieu va tcvn

8/12/2019 Phep Thu Cho Diem Thi Hieu Va Tcvn

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4.2.4. Php thmc chp nhn (consumer acceptance test)- Php th

cho im thhiu

Mc ch

Xc nh mc a thch hay kh nng chp nhn ca ngi tiu dng

i vi cc sn phm nh gi.

Nguyn tc

Cc mu c phc v theo trt t ngu nhin.Ngi th th nm tng

mu theo th t t tri sang phi v cho bit mc a thch ca h i vi

tng mu trn thang im th hiu

Cch tin hnh php th

Mu thS lng mu th ty thuc vo mc phc tp v tnh cht ca mu

ging nh trong php th xp dy.

Cc mu c trnh by theo trt t hnh vung Latin Williams (ph lc

1).

Ngi thNgi th l ngi tiu dng c kinh nghim s dng sn phm, cha qua

hun luyn. Ngi th c nhim v cho im trn thang im theo s thch ca

mnh, do y cng l mt nhc im ca php th cho im th hiu. Bi v

mi ngi th c mt s thch khc nhau, hay ni cch khc l khung i chiu

khc nhau. V vy, khi cho im, ngi th da trn khung i chiu ca mnh

t a ra cc kt qu m c th l cng s im nhng ngha ca n li

hon ton khc nhau. Do , lng ngi th cho php th ny cng ln cng

tt v i km theophp th mc chp nhn lun lun l mt bng cu hi

thu nhn thng tin v thi quen tiu dng hay quan im, hay cm xc ca

ngi tiu dng. T bng cu hi kt hp vi d liu cm quan mi cho ta thy

c ci nhn tng qut v ngi tiu dng, phn nhm ngi tiu dng v c


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lch bnh phng do sai s. Do , t s gia phng sai ca nhn t v phng

sai ca sai s c gi l gi tr F hay l Ftest. Gi tr F ny biu th s bin thin

gp ca cc tr trung bnh ca nhn t c quan tm so vi tr trung b nh chung

ca tp hp d liu, chia cho sai s trung bnh bnh phng. y l gi tr chnh

trong phn tch phng sai.

C 2 gi thuyt:

- H0(null hypothesis): khng c s khc bit gia cc mu th (sn phm).

- HA(Alternative hypothesis): c s khc bit ng k gia cc mu th (sn

phm).

Bng 4.4. Bng ANOVA ca phn tch phng sai theo mt yu t

(one way within subject)

Ngun ca sbin ng

t do(df)

Tng cc bnhphng (SS)

Trung bnh

bnh phng(MS)

Gi tr F

Sn phm(A) a-1 SSA MSA MSA/ MSAS

Ngith(S) s-1 SSS MSS

S*A (phn d) (a-1)(s-1) SSAS MSAS

Tng as-1 SStotal

a: s sn phm (mu th)

s: s thnh vin hi ng(ngi th)

tnh ra c gi tr F, ngi ta bin i thng qua cc cng thc tnh

ton nh sau:

1. Tng bnh phngTngbnh phng ca sn phm (A):

= (...)Tng bnh phng ca ngi th (S): = (. ..)

Tng bnh phng caphn d(AS)


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=( . .+..)2. Trung bnh bnh phngTrung bnh bnh phng mu:

= 1Trung bnh bnh phng ca ngi th:

= 1Trung bnh bnh phng caphn d:

= (

1) (

1)

3. Tng quan phng saimu(F) =

Tra bng phn b F (Bng 12, ph lc 2)ng vi bc t do ca sn phm v bc

t do ca sai s v so snh gi tr Ftnh

Nu Ftnh Ftra bng: Chp nhn gi thuyt HA Nu Ftnh< Ftra bng: Chp nhn gi thuyt H0

- Nu tnh gi trF v cho thy rng tn ti mt skhc bit c ngha gia cc

sn phm (t 3 sn phm tr ln), chng ta cn phi xc nh c thcc mu

no c skhc bit vi nhau bng cch tnh gi trskhc bit nhnht LSD

(Least Significant Difference) mc ngha 5%.

Cng thc tnh gi tr LSD nh sau:

= 2 Trong : t l gi tr ti hn t cho php kim nh hai pha (tra bng 10, ph

lc 2)ng vi bc t do ca sai s.


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- Tip theo tnh hiu s gi tr trung bnh ln lt gia cc sn phm v so snh

vi gi tr LSD.

+Nu hiu s gi tr trung bnh nh hn gi tr LSD th gia 2 sn phm

khngkhc nhau mc ngha 5%.

+Nu hiu s gi tr trung bnh ln hn gi tr LSD th gia 2 sn phm

c s khc nhau c ngha mc ngha 5%.

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