crime. Figure 2A-7,
cheap zumba dvd, however,
new beats by dr dre, is not based on such an experiment. We simply ob-
serve that more dangerous cities have more police officers. The explanation for this
may be that more dangerous cities hire more police. In other words,
dior shoes 2011, rather than
police causing crime,
wholesale Tampa Bay Lightning jerseys, crime may cause police. Nothing in the graph itself allows us
to establish the direction of causality.
It might seem that an easy way to determine the direction of causality is to
examine which variable moves first. If we see crime increase and then the police
force expand, we reach one conclusion. If we see the police force expand and then
crime increase,
plus size true religion jeans, we reach the other. Yet there is also a flaw with this approach: