Did airbags, over 1997-2002 in the US, reduce accident risk?

For further details

(1) see <URL: http://www.stat.uga.edu/~mmeyer/airbags.htm>

(2) install the package DAAGxtras from the Comprehensive R 
Archive Network, attach the package, and type help(excessRisk)
and help(nassCDS).

Notes: 
1) nassCDS has a subset of the columns of nass9702cor.  The columns dvcat,
dead, airbag, seatbelt, sex have been turned into factors with meaningful
level names.

2) In the column 'dead' nass9702cor, 1 denotes dead, 2 denotes alive

3) The data frame 'nasshead' has one row  for each column in nass9702cor.
The column 'shortname' is the name used in nass9702cor.  The column 
'SASname' has the name used in the SAS transport file.  The column
'longname' has a more complete description, again taken from the SAS
transport file.