. Author manuscript; available in PMC: 2013 Aug 8.

Published in final edited form as: Occup Environ Med. 2010 Dec 30;68(6):414–418. doi: 10.1136/oem.2010.055905

Table 2.

Average rate of hearing loss (dB/year) before and after initiation of daily noise exposure monitoring

	Intervention group			Control group			Difference in difference^*	p Value
	No.	Before	After	No.	Before	After	Difference in difference^*	p Value
All intervention subjects	80	1.7 (1.3)	−0.5 (1.9)
Matched on age, gender, baseline hearing	78	1.8 (1.3)	−0.4 (1.5)	234	0.4 (1.1)	−0.1 (2.1)	1.7	<0.0001
Matched on age, gender, baseline hearing and initial rate of hearing loss	46	1.4 (1.5)	−0.2 (1.6)	138	1.1 (1.1)	0.45 (1.45)	1.0	0.06

Difference in the difference between the pre-intervention (2000–2004) and post-intervention time periods (2006–2010).