Table 1.

Study designs for evaluating interventions on occupational diseases or injuries

Outcome measure	Shorter latency∗ ≤12 mo	Longer latency >12 mo
Higher frequency† > 5%	Randomized controlled trials Indication for effect: strongest Example 1	Controlled studies Indication for effect: moderate Example 2
Lower frequency ≤ 5%	Interrupted time series Indication for effect: low Example 3	Time series, case series Indication for effect: weakest Example 4

^∗Latency: time interval between exposure to hazardous agents or work demands and occurrence of diseases or injuries.

^†Frequency: number of diseases or injuries in a population over a time period.