Table 3. Duration of tubes by groups.

Duration of tubes (months)	Group A		Group B		Total
	No.	%	No.	%	No.	%
3	2	4.9	7	12.5	9	9.3
4	3	7.3	15	26.8	18	18.6
5	19	46.3	21	37.5	40	41.2
6	17	41.5	13	23.2	30	30.9
Total	41	100	56	100	97	100
Mean duration of tubes	5.2	-	4.7	-	4.9	-
SD	0.8	-	1.0	-	0.9	-
VC	15.1	-	20.3	-	18.8	-
T test=2.64; DF=95; P=0.0097*