Note on construction of an item analysis table for the high-low-27-per-cent group method

This paper describes the construction of a new item analysis table for the high-low-27-per-cent group method. The table provides a ready means of translating the observed proportions of success in the two extreme groups (p _H ,p _L ) into measures of item difficulty and item discrimination (p, Δ, andr). The tabled values of both the difficulty index,p, and the discrimination index,r, have been derived from Karl Pearson's tables of the normal bivariate surface.