After the normals and psychiatric patients had been administered the 504-item scale, Hathaway and McKinley could then compare their responses.
Each item that cor- rectly differentiated between these two groups was included in the resulting clinical scale.
For example, item 40, "Much of the time my head seems to hurt all over," was answered "True" by 120/0 of the sample of hypochondriacs and by only 4% of the normal.
It was thus included in the clinical scale for hypochondriasis.
The comparisons, then, were between each clinical group and the group of nor mal s rather than among the different clinical groups themselves. This was the selection procedure used to develop tentative clinical scales.