confident that the actual rate of overblocking in that particular
library falls. We note that these confidence intervals assume
that the time period for which the study assessed the library's
internet logs constitutes a random and representative sample.
To illustrate the two different methods, consider a
random sample of 1010 web sites taken from a library's Internet
use log, 10 of which fall within the category that a filter is
intended to block (e.g., pornography), and suppose that the
filter incorrectly failed to block 2 of the 10 sites that it
should have blocked and did not block any sites that should not
have been blocked. The standard method of quantifying the rate
of underblocking would divide the number of sites in the sample
that the filter incorrectly failed to block by the number of
sites in the sample that the filter should have blocked, yielding
an underblocking rate in this example of 20%. Finnell's study,
however, calculated the underblocking rate by dividing the number
of sites that the filter incorrectly failed to block by the total
number of sites in the sample that were not blocked (whether
correctly or incorrectly) yielding an underblocking rate in this
example of only .2%.
According to Biek, the sample size that he used yielded a
95% confidence interval of plus or minus 3.11%.
Edelman is a Harvard University student and a systems
administrator and multimedia specialist at the Berkman Center for
Internet and Society at Harvard Law School. Despite Edelman's
young age, he has been doing consulting work on Internet-related
issues for nine years, since he was in junior high school.
The archiving process in some cases took up to 48 hours
from when the page was blocked.
In October 2001, Edelman published the results of his