17. [
Overes.ma.ng
unique
visitors
]
The
study
examined
data
from
two
of
the
UK’s
busiest
ecommerce
websites,
ASDA
and
William
Hill.
Given
that
more
than
half
of
all
page
impressions
on
these
sites
are
from
logged-‐in
users,
they
provided
a
robust
sample
to
compare
IP-‐based
and
cookie-‐based
analysis
against.
The
results
were
staggering,
for
example
an
IP-‐based
approach
overes3mated
visitors
by
up
to
7.6
3mes
whilst
a
cookie-‐based
approach
overes.mated
visitors
by
up
to
2.3
.mes.
Google:
”red
eye
cookie
report
pdf”
or
hMp://bit.ly/cszp2o
Source:
White
Paper,
RedEye,
2007