Key terms and symbols

ability parameter (1s)

agreement statistic

B-index

bimodal

central tendency

difference index (DI)

domain score

guessing parameter (ci)

instructed

intervention strategy

item characteristic curve (ICC)

item difficulty parameter (bi)

item discrimination (ID)

item discrimination parameter (ai)

item facility (IF)

item information function (IIF)

item phi (Ø)

item response theory (IRT)

masters

mean (M)

median

mode

negatively skewed

non-masters

number of students (N)

number of items (k)

one-parameter model

percentage

percentile

positively skewed

range

Rasch model

standard deviation (S)

three-parameter model

trimodal

two-parameter model