I am conducting a mixed-methods study. From my quantitative data (n=254), I am identifying potential participants for group interviews.

The eligibility criteria for the interviews involves high body dissatisfaction, low drive for thinness, and low bulimia tendencies. These variables were measured using the EDI-3 (valid and reliable). Each variable has a cut off score to indicate high vs. low risk. Using the established cut off scores, only 16 participants meet my criteria for the interviews. I need to expand this, so I would like to open up the cut off scores a bit. What approach should I use? Do I simply change the cut off score (for example, if the original scale is 1-16 for low drive for thinness, do I look at 1-17)? Do I calculate my standard deviations and then multiply the cut off scores by .5 SD?

Any help is appreciated!