Kellogg community college nursing student handbook

Sometimes the content of a question may be judged to be so important that it is included in the
exam for the purpose of reinforcing the concept. Such items are often referred to as mastery
items, and they should be identified before the test is administered. Simply because 100% of the
students answered an item correctly does not mean it is a mastery item; it may just be too easy.
Also, identifying mastery items prior to administering an exam allows students’ knowledge of
students’ knowledge of essential content to be evaluated. If only a few of the students answer a
mastery item correctly, then the class as a whole does not understand the content, and it should
be re-taught.
Caputi, L., Engelmann, L. (2011). Teaching Nursing: The Art and Science. College of DuPage
Item Discrimination
Point Biserial Correlation Coefficient (PBCC)
The point biserial correlation coefficient (PBCC) is a calculation that measures the ability of a test
item to distinguish between those who know the content and those who do not know the content.
The point biserial correlation coeffient calculation is the preferred measure of discrimination as it
includes the variance of the entire group, not just the high and low-scoring students. The PBCC
ranges from -1 to +1. The closer the PBCC is to +1, the better the item is at discriminating
between those students who know and those who do not. A negative discriminator indicates that
the lower- scoring students answered the item correctly more often than higher-scoring students.
An acceptable PBCC described in the literature is 0.20 (Haladyna, 1997). Because a group of
nursing students is often more homogenous because they have the same prerequisites to enter a
particular nursing program, less variance exist among the group members. Therefore, a lower
PBCC of 0.15 is acceptable in schools of nursing. Based on this knowledge, PBCC levels or 0.15
and higher are acceptable (Morrison et all., 1996).
Range for PBCC
Range from -1 to +1
0.30 - & above – Excellent Item
0.20 – 0.29 – Good
0.15 – 0.19 – Acceptable
0.10 – 0.14 Poor & Revise
(Sportsman, 2013)
Actions for Poor Test Items
The following information is recommended for use in determining what action to take for poor test
items:
1. PBCC unacceptable & p value < 0.30 = give credit for more than one answer, work on
question to improve.
2. PBCC acceptable & p value > 0.30 = do nothing, the question is OK
3. PBCC unacceptable & p value > 0.30 = do not give points back, work on the question to
improve.
4. PBCC acceptable & p value < 0.30 = do not nullify or give points, revisit the concept in class as
students did not grasp the concept.
(Sportsman, 2013)
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