These data, collected in Florida between 1968 and 1971, were collected 
in a randomized study to see whether massive injections of silver 
iodide into cumulus clouds can lead to increased rainfall.  On each of 
52 days deemed suitable for seeding, a randomizing device was used to 
decide whether to seed the target cloud or not.  An airplane flew 
though the cloud regardless of whether the cloud was seeded and the 
pilots were unaware of whether the seeding mechanism was loaded.  The 
data set (one record per cloud) contains the total rainfall as 
measured by radar (RAIN) and whether the cloud was seeded (1=yes, 
0=no).  Did cloud seeding have an effect on rainfall?  If so, by how 
much?