Introduction to Epidemiology 6th Edition by Ray M Merrill

Exercise 14

Suppose 45 traffic accidents occur on a given road and you are interested in measuring whether the accidents are associated with rain showers. The “case” period is designated as the 24 hours preceding the accident and the “control” period is designated as 1 week prior to the case period. Among the accident cases, 7 experienced rain showers during the case and control periods; 16 experienced rain during the case period but not during the control period; 4 experienced no rain during the case period but rain during the control period; and 18 experienced no rain during either the case or control periods. Use an appropriate measure and describe whether an association exists between particulate matter and cardiac events.

Step 1 of 5

Odds ratio (OR) which is also known as the relative ratio which is used as a measure for comparative probabilities of events in case control studies.

• When the odds ratio (OR) is equal to one then there is no connection between event and the condition,

• If OR is greater than 1 then there is positive connection between the event and the condition,

• if OR is less than 1 then it is negative connection between the event and the condition.