A Researcher Wishes to Establish the DI (Discrimination Index) for a Series

A researcher wishes to establish the DI (Discrimination Index) for a series of five items contained in a new test being developed to assess Whole Language Readiness (WLR). The data are as follows: Item Proportion Correct Proportion Correct $\quad$ $\quad$ $\quad$$\begin{array}{llcc}\text { For Top Third}& \text { For Bottom Third }\end{array}$

a. $\quad$ $\quad$ $\quad$ $\quad$ .70 $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ .60

b. $\quad$ $\quad$ $\quad$ $\quad$ .70 $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ .50

c. $\quad$ $\quad$ $\quad$ $\quad$ .50 $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ .20

d. $\quad$ $\quad$ $\quad$ $\quad$ .95 $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ .70

e. $\quad$ $\quad$ $\quad$ $\quad$ .45 $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ .50 For Top Third For Bottom Third