Obtain the test characteristic curve for a test with five items using the following item difficulty and item discrimination parameters:

b1 D 0:0 b2 D 0:0 b3 D 0:0 b4 D 0:0 b5 D 0:0 a1 D 0:4 a2 D 0:8 a3 D 0:4 a4 D 0:8 a5 D 0:4 The test characteristic curve is nearly a straight line with a rather shallow slope reflecting the low to moderate values of

a. The mid true score of 2:5 occurs, as expected, at an ability level of 0:0.