Table 3. Relationship of periodontitis with age and various parameters of tobacco smoking.

	Periodontitis	Sample (n)	Mean±S.D.	Standard error mean	P
Age (years)	Yes	372	41±13.359	0.693	<0.001
	No	150	26±9.063	0.740
Years of smoking	Yes	119	14.36±11.303	1.036	<0.001
	No	19	7.15±4.003	0.918
Cigarettes per day	Yes	119	7.82±7.091	0.650	0.429
	No	19	6.47±5.004	1.148
Pack years of smoking	Yes	119	6.25±8.594	0.787	<0.001
	No	19	2.45±2.501	0.573

Independent samples t-test (2-tailed) at confidence interval 95%