The 
ichael Project
Tian Zheng, Matt Salganik, Andrew Gelman
Introduction: Recently
a survey was taken of Americans, asking, among other things, ``How many males
do you know incarcerated in state or federal prison?'' The mean of the responses to this question
was 1.0. To readers of this journal that
number may seem shockingly high. We
would guess that you probably don't know anyone in prison. In fact, we would
guess that most of your friends don't know anyone in prison either. This number may
seem totally incompatible with your social world.
So
how was the mean of the responses 1? According to the data, 70% of the
respondents reported knowing zero people in prison. However, the responses show
a wide range of variation, with almost 3% reporting that they know at least 10
prisoners. Responses to some other questions of the same format, for example “How
many people do you know named Nicole?” show much less variation.
This
difference in the variability of responses to these "how many people do
you know" questions is the manifestation of fundamental social processes
at work. Through careful examination of
this pattern, as well as others in the data, we can learn about important characteristics
of the social network connecting Americans, as well as the processes that
create this network. This analysis also furthers our understanding of
statistical models from two-way data.