THE PAIRED AVAILABILITY DESIGN - A PROPOSAL FOR EVALUATING EPIDURAL ANALGESIA DURING LABOR

The paired availability design (PAD) can reduce selection bias when it is not possible to randomize subjects. PAD consists of independent pa irs of experimental and control groups. Within each pair, the interven tion is the availability of treatment not its receipt. In the experime ntal group, the new treatment is made available to all subjects althou gh some may not receive it. In the control group, the experimental tre atment is generally not available to subjects although some may receiv e it in special circumstances. We present a statistic to test a null h ypothesis that the receipt of intervention will increase response by a specified non-zero amount delta. We propose this design for use in a study of the effect of epidural analgesia on the rate of Caesarean sec tion.