Thank you Adina:)
The development of a reliable and valid measure of BPI is part-1 of this PhD project.
The BPI measure(which we systematically developed) is a 20 items scale tapping how strongly or weakly participants believe their emotional and thought components affect their illness recovery(Scale paper is coming soon as a journal article). The theoretical concept of BPI is first elaborated by Professor Thomas Gilovich. We based on that theoretical concept to develop the measure.
Out of the 20 items , we estimate a composite continous score ranging from 0(low BPI) to 1(High BPI).Regardless of participants educational background, sex and age-BPI is fairly normaly distributed among the sample. In addition, it is highly correlated with religousity. As a continuation of the scale development, we also made few experiments to check whether it could be possible to manipulate BPI by priming it. That was successful too.