Table 3 Result of analysis of covariance on the effect of intervention on pain intensity with control the confounder variables

Score of Pain after first intervention

Infrared belt group

-19.000

.932

-20.377

 < 0.001

Hot water bag group

-7.434

.884

-8.407

 < 0.001

Control group

0^a

Score of Pain at admission

.649

.054

12.087

 < 0.001

Score of Pain after second intervention

Infrared belt group

-21.632

1.199

-18.037

 < 0.001

Hot water bag group

-8.192

1.137

-7.202

 < 0.001

Control group

0^a

Score of Pain at admission

.488

.069

7.075

 < 0.001

Score of Pain at the end of first stage of labor

Infrared belt group

-13.114

1.385

-9.468

 < 0.001

Hot water bag group

-5.009

1.313

-3.814

 < 0.001

Control group

0^a

Score of Pain at admission

.310

.080

3.894

 < 0.001