Introduction to Epidemiology 6th Edition by Ray M Merrill

Exercise 1

Calculate the attack rates for the various amounts of water consumption as it relates to illness onset, found in Table 1.

Table 1 Attack Rates of Gastrointestinal Illness by Usual Amount of Water Consumed Daily at the Middle School

Estimated Amount of Water Drunk	Students		Faculty
	No. III/Total	Attack Rate (%)	No. III/Total	Attack Rate (%)
0 glasses	4/11		3/3
1 glass	14/19		2/5
2 glasses	24/36		1/2
3 glasses	38/57		1/3
4 glasses	43/56		2/2
5 glasses	28/38		0/1
6+ glasses	43/50		3/3

Step 1 of 3

Attack rate can be defined as the rate of number of diseased cases to the number of individual that are followed or at risk.