The effect of using a 30% cutoff for the proportion of HER2+ cells on the interobserver variability in the interpretation of HER2 immunohistochemical results was evaluated. Immunostained sections from 96 cases of breast carcinoma were reviewed by 10 pathologists and scored as positive (3+) when uniform strong membranous staining was identified in at least 10% of tumor cells; the actual percenta...

Regression discontinuity designs (RDD) assign participants to conditions using a cutoff score, with those above the cutoff going to one condition and those below to another. Statistical theory shows that a correctly implemented and analyzed RDD gives unbiased effect estimates, just as in a randomized experiment. This study tests that theory by randomly assigning 588 participants to be in a rand...