Abstract
Andy Sadler and Larry Lang (2006)
"Using Survival Analysis To Predict Sample
Retention Rates"
The International Price Program (IPP) publishes monthly price indexes
which measure the average change over time in prices of internationally
traded products and services. IPP's sampling methodology supports
its published merchandise price indexes by attempting to maintain a
minimum number of items, within each published stratum, over the
stratum's two year life cycle. Stratum retention rates — formerly calculated
by using an averaging process — are used to set minimum item allocations.
This paper uses the Life-Table estimate of the survivor function
applied to censored data to model retention rates. Our conclusions
are: (1) The model produces a markedly superior fit to that produced
from using simple averages; (2) The model is un-affected when samples
are rotated; (3) The model allows us to use the Lower Confidence Limit
which gives conservative estimates of the survival rates
Last Modified Date: January 9, 2007
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