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FREQUENTLY ASKED
QUESTIONS
REPLICATES
During the preliminary data period, the term
“replicate” will be used as a way of describing the incremental increase of
the LPM sample size, as the launch date approaches. The following are some
pointers in understanding what replicates are and how they affect the
sample.
WHAT IS A REPLICATE?
A sample replicate is a smaller version of the full sample. The full sample
is selected from the DMA universe, based on a specific sample design.
Smaller samples are then selected from the full sample, using that same
sample design. These smaller samples are called replicates.
Replicates are utilized to achieve a representative sample prior to
installation of the full sample, which in turn allows reporting of estimates
prior to installation of the full sample (in this case referred to as our
Preliminary Data Period).
IN THE LPM EXPANSION PLANS, HOW MANY REPLICATES
WILL BE USED TO BUILD THE FINAL SAMPLE?
It depends on the sample. In Los Angeles, New York, and Chicago, there will
be three replicates; the sample size will start at 540 HHs (Replicate 1),
then increase to 640 HHs (Replicate 2), then increase to 800 HHs (Replicate
3). In San Francisco, there will be two replicates; the sample size will
start at 640 HHs (Replicate 1) and then increase to 800 HHs (Replicate 2).
HOW ARE REPLICATE SIZES DETERMINED?
Replicate sizes are measured in terms of specs issued to our Field staff.
This will vary slightly from market to market, based on the census vacancy
rate in the market. In Los Angeles, Replicate 1 has 675 specs, Replicate 2
has 125 specs, and Replicate 3 has 200 specs. In New York, the spec sizes
are 680, 125, and 200, respectively. In Chicago, the spec sizes are 675,
125, and 195. In San Francisco, Replicate 1 has 810 specs and Replicate 2
has 200 specs.
HOW DOES THE INCORPORATION OF ADDITIONAL REPLICATES
INTO THE SAMPLE AFFECT THE SAMPLE CHARACTERISTICS OR THE VIEWING ESTIMATES?
Each replicate is selected using the overall sample design, therefore
changes in sample characteristics or viewing estimates that occur after a
replicate has been added are due to a reduction in sampling error.
Specifically, as each replicate is added, the overall sample size (as well
as the sample size of each characteristic) increases, and the sampling error
for the viewing estimates goes down.
AT WHAT POINT WILL THE LAST REPLICATE BE
INCORPORATED INTO THE SAMPLE, SO THAT THE FINAL SAMPLE SIZE IS REACHED?
The final replicate is added into the sample just prior to the “launch” date
for each market.
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