Information Technology Reference
In-Depth Information
Shaikh, Baker, and Russell (2004) used an efficiency metric based on the
number of clicks to accomplish the same task on three different weight-loss
sites: Atkins, Jenny Craig, and Weight Watchers. They found that users were sig-
nificantly more efficient (needed fewer clicks) with the Atkins site than with the
Jenny Craig or Weight Watchers sites.
LOSTNESS
Another measure of efficiency sometimes used in studying behavior on the web
is called “lostness” (Smith, 1996). Lostness is calculated using three values:
N
: The number of
different
web pages visited while performing the task
S
: The
total
number of pages visited while performing the task, counting
revisits to the same page
R
: The
minimum
(optimum) number of pages that must be visited to accom-
plish the task
Lostness,
L
, is then calculated using the following formula:
2
2
L
= sqrt[(
N S
/
-
)+ (/
R N
-
1) ]
.
Consider the example shown in
Figure 4.7
. In this case, the user's task is to
find something on Product Page C1. Starting on the home page, the minimum
number of page visits (
R
) to accomplish this task is three. However,
Figure 4.8
illustrates the path a particular user took in getting to that target item. This user
started down some incorrect paths before finally getting to the right place, visit-
ing a total of six different pages (
N
), or a total of nine page visits (
S
). So for this
example:
N
= 6
S
= 9
R
= 3
2
2
L
=
sqrt[(6/91)
-
+
(36 1) ]
/ -
=
00
.
6
Home
Page
1
Category
Page A
Category
Page B
Category
Page C
2
Product
Page A1
Product
Page A2
Product
Page A3
Product
Page B1
Product
Page B2
Product
Page B3
Product
Page C1
Product
Page C2
Product
Page C3
3
Figure 4.7 Optimum number of steps (three) to accomplish a task that involves finding a target item on
Product Page C1 starting from the home page.
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