Parameters Ordinal scale ratings (mean rank) in six groups N Chi-Square Df Pb
value
1 2 3 4 5 6
Lamina dura delineation 3.08 3.58 3.58 3.58 3.58 3.58 6 5.00 5 0.42c
Trabecular pattern depiction 2.33 3.25 3.25 3.75 3.75 4.67 6 8.63 5 0.13c
Contrast perception 3.00 3.00 3.00 3.50 4.50 4.00 6 7.50 5 0.19c
Bone crater involvement 3.33 3.33 3.33 3.33 3.83 3.83 6 1.11 5 0.95c
Furcation defect involvement 2.83 2.33 3.83 3.33 4.33 4.33 6 8.00 5 0.16c

aSix groups are combination of two kV settings and three exposure times: 1 = 70 kV, 80 ms; 2 = 63, kV 80 ms; 3 = 70 kV, 120 ms; 4 = 63 kV, 120 ms; 5 = 70 kV, 160 ms; 6 = 63 kV, 160 ms.
bTested between the groups.
cThe mean differences are not significant at 95% significance level.
Df = degree of freedom.