In this investigation, a sample of 158 persons who had eaten in the cafetertia were interviewed for food histories as well as illness histories were taken.

The sample included both persons who had been ill and persons who had not.

Among those interviewed 99 (63%) had been ill.

The attack rate table constructed during

Time Data Pattern:

Total number at risk	158
Total no. affected day (0)	0
Total no. affected	99
Total no. unaffected	59