­­­­­
Original
Message­­­­­
From:
Rushneck,
Dale
NE
Sent:
Monday,
February
03,
2003
11:
58
AM
To:
Leonid
Kopylev;
Miller,
Ken;
Cuddeback,
Joan;
Bill
Telliard;
Khouane
Ditthavong;
McCarty,
Chip;
Riddick,
Lynn;
Henry
Kahn;
Maria
Gomez­
Taylor
Subject:
Fw:
Replicates
for
MDL
E­
mail
from
John
Glaser
below,
so
that
the
record
on
7
replicates
for
the
MDL
is
complete.

dale.
rushneck@
attbi.
com
Phone:
970­
223­
2013
Fax:
970­
223­
2008
­­­­­
Original
Message
­­­­­
From:
<
Glaser.
John@
epamail.
epa.
gov>
To:
"
Dale
Rushneck"
<
dale.
rushneck@
attbi.
com>
Sent:
Monday,
February
03,
2003
9:
20
AM
Subject:
Re:
Replicates
for
MDL
Dale
I
agree
that
your
have
captured
most
of
the
discussion.
Bill
Budde
also
agrees
with
the
points
that
you
have
identified.
One
salient
feature,
that
I
believe
to
be
important
to
the
discussion,
is
that
the
detection
limit
is
an
assessment
of
the
noise
in
the
analytical
system.
The
noise
is
dynamic
and
can
vary
widely
with
sample
composition.
Our
selection
of
7
reps
is
also
based
on
these
considerations.
Our
philosophy
recognizes
that
detection
limits
are
characteristics
of
an
analytical
procedure
and
as
such
show
what
analytical
power
the
procedure
possesses.

Regards
John
A.
Glaser,
Ph.
D.
Leader,
Sustainable
Technology
Team
USEPA
National
Risk
Management
Research
Laboratory
26
W.
King
Dr.
Cincinnati,
OH
45268
513­
569­
7568(
voice)
513­
487­
2511(
fax)

­­­­­
Original
Message
­­­­­
Date:
02/
02/
03
06:
25
PM
From:
Dale
Rushneck
<
dale.
rushneck@
attbi.
com>
To:
John
Glaser/
CI/
USEPA/
US@
EPA
cc:
Henry
Kahn/
DC/
USEPA/
US@
EPA
Subject:
Replicates
for
MDL
Hi
John
I
spoke
with
you
last
September
on
the
subject
number
of
replicates.
I
am
a
contractor
assisting
EPA
with
test
procedures
and
regulations.

EPA
wants
to
include
a
reference
to
your
statements
in
the
Assessment
Document
that
supports
re­
assessment
of
detection
and
quantitation
procedures.
However,
rather
than
use
my
paraphrasing
of
your
statements,
I
thought
I'd
send
you
an
e­
mail
and
have
you
correct/
re­
word
my
paraphrasing
so
that
I
do
not
misquote
you.
The
following
are
my
notes
from
our
conversation.
Please
correct/
revise
as
appropriate
and
send
me
your
changes
by
return
e­
mail.

Thanks
Dale
dale.
rushneck@
attbi.
com
Phone:
970­
223­
2013
Fax:
970­
223­
2008
­­­­­
This
file
documents
a
phone
conversation
between
Dale
Rushneck
and
John
Glaser
on
9/
25/
02
I
called
John
to
ask
how
the
number
7
was
established
for
replicates
in
the
MDL
procedure.
John
stated
the
following:

1.
It
was
chosen
for
statistical
power.
The
statisticians
wanted
a
number
that
would
be
representative.

2.
7
is
the
breakpoint
in
the
t
statistic.
Below
7
replicates,
the
students'
t
multiplier
becomes
large;
above
7
it
begins
to
approach
an
asymptote.

3.
There
is
nothing
magical
about
7;
it
was
chosen
as
a
compromise
between
having
too
few
analyses
to
satisfy
the
statisticians
and
too
many
analyses
to
be
practical
for
the
analytical
chemists.

4.
7
was
also
estimated
to
be
cost
effective.
