In 1978, a small plane slammed into a passenger jet over San Diego,
killing 144 people. Langhorne Bond, then the head of the FAA,
responded by proposing strict new curbs on small planes around many
busy airports. Examine the following FAA data. Is there a
statistically significant difference in the frequency of different
types of near midair collisions between the first 6 months of 1985 and
the first 6 months of 1986? Why? A corporate plane in this case, means
a UPS or FEDEX type of aircraft.


Type of Incident Jan-July ?85		              Jan-July ?86
		        O	        E	       O	E
2 airliners	       15	      16.6	       19	17.4

1 airliner and 
1 corporate plane	99		112		130	117

2 corporate planes	262		247.4		244	258.6

TOTAL			376				393

To make a calculation of this, one would need to know the total volume
of air traffic in the two categories for the two periods for the same
set of airports as the FAA numbers.