Japanese Students’ Behavior Toward E-Commerce - IT Enabled Services - page 184

Table 11.10 Variety and
level of an attribute

Attribute Level 1 Level 2 Level 3

Store Yes No -

Saturation High Low -

Procedure Easy Difficult -

Postage Free 500 yen -

Price 3,000 yen 4,000 yen 5,000 yen

e mV ni
j2C

P ni ¼ (11.3)

e mV nj

However, CL is the model achieved under two assumptions, homogeneous
preference and Independence from Irrelevant Alternatives : IIA . Although CL is
easy to analyze, it has the problem of weak model interpretability. Revelt and Train
( 1998 ) advocated the mixed logit model ML, which eliminates these two
assumptions. ML is a model that has a preference from which an individual differs.
When a certain respondent n chooses item i , utility is set to U ni , denoted as follows.

X

M
m¼ 1 b

m

n x ni þ e ni

U ni ¼ V ni þ e ni ¼ (11.4)

e ni has an independent and identical type I extreme value
distribution, and the probability that the respondent n will choose i is formulized as
follows.

It is assumed that

ð Y

T

V i Þ
P j ¼ 1 exp

exp ð

P ni ¼ f ðbj O Þ d b (11.5)

ð V j Þ

t 1

T indicates the number of occurrences of the choice experiment, and several
repetitive questions are presented to the same respondent in the usual choice
experiment. f is the probability density function of

b

, and O indicates parameters

such as the average and variance of .

In this study, the choice experiment was conducted using an orthogonal array
design; the variety of attributes and the level were set up as shown in Table 11.10 .
Eight profiles were created using the orthogonal array design from the level of
each attribute. Two profiles were combined at random, and a choice set with the
added option “Using neither online shop” was created. Each respondent answered
eight choice sets per questionnaire. An example of a choice set is shown in
Table 11.11 .
An alternative specific constant (ASC) was added to the analysis; ASC3 was
introduced into “Using neither online shop.” It can be interpreted as negative for the
purchase of goods from an online shop if the ASC is significantly estimated as

b