Dear all:

The article that was mentioned about test weighing is deeply flawed because it bases the whole 
premise of test weighing on a false premise - that reading the lines on bottles is the gold standard 
for reality.  In this case, their assumption that reading the volume of a liquid from a bottle is a 
gold standard defies any scientific training I have had since my first chemistry class.

Here are the flaws in this assumption:

1) The meniscus - I am probably mispelling this, but I remember this from my high school 
chemistry teacher who I had a crush on because he looked like Einstein and was brillant.  When 
you look at any liquid in a container, there is water tension that creates a dip in the surface of the 
liquid; that is to say the liquid will be higher on the sides of the container than in the middle.  The 
size of the container, the composition of the liquid, the temperature of the room, can all influence 
the degree to which the liquid will cling to the sides.  You should always read the dip.  So, I see a 
huge amount of variation that can creep in from reading the volume of liquid by eyeballing the 
bottom of the meniscus against a line on the bottle.  Even if your eyes are slightly higher or lower 
than the meniscus can influence what volume you read.

2) The dribble factor.  I can tell you from my vast experience in weighing everything in sight (I use 
the scale sometimes as a wake up device and my curiousity drives me to stealthily weigh all sorts 
of things when parents are totally unaware that I'm doing so) that babies dribble to varying 
degrees and you sometimes lose that dribble.  I've lost as much as 0.5 oz with some babies that 
are on the profuse end of the dribble spectrum (and those are the ones that often really should  
not be drinking from a bottle).  

3) The difference in response to flow.  We all know that babies feed differently from the breast 
than they do from other devices.  You cannot compare how they feed from one device with the 
breast.  Why anyone would think that this tests how a baby feeds at the breast is beyond my 
conception.

The equivalent that I see in the dietary world is testing what people eat.   You have a variety of 
different ways to estimate intake - 24 hour recalls, 3 day recalls, food diaries, weighing and 
measuring the food that is eaten.  None of these can be taken as the "true gold standard" because 
the process of doing the measurement influences how people eat.  The 24 hour recall can be 
influenced by fluctuations in diet from day to day.  The 3 day recall may be more subject to 
forgeting items that were eaten than trying to just remember the last 24 hours.  A food diary may 
come closer to documenting what is eaten at the time you eat it, but there is nothing like having 
to write down that you ate a whole box of cookies and having someone else read what a pig you 
were to make you stop and eat fewer cookies than you would have if you weren't recording what 
you ate.  

The advantage of the scale is that you can test this on objects of known weights and determine 
very precisely what the range of variation is.  When they say the range is 0.1 oz and the scale is 
calibrated that is the range.  

As far as I know, no one has calibrated the range for eyeballing the quantity of milk in a bottle!  
Plus, there is always that little dribble left in the bottom of the bottle that won't come out.  

What the study shows from my perspective is how much variation there is in eyeballing a bottle, 
not the other way around.

Best regards, Susan Burger

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