Effectiveness of the Test Item

Sometime, as part of the accreditation processes it may be required to know the level of the test items. Is there any way of finding whether the test item asked in an examination is good enough to distinguish between a good and a weak student. Or it may be required to know whether the question is easy enough so that every student weak or good is able to answer it, or no one or most of the student are not able to answer. The analysis of the result may reveal some information that is being discussed in this blog. I present these two terms as the facilitation value and the discrimination value which are elaborated in the following section.

In this process about 60% of the student are tested for their performance in an examination. This sample is quite large to deduce about the level of the question. The steps involved are:

a.       Tabulate the marks of the test item and the score for all question by all students.

b.      Sum total the marks in all test items.

c.       Arrange the list in ascending order based on the total marks scored.

d.      Take 30% of total as the upper group and 30% as the lower group students.

The above tabulation is useful to calculate the facilitation and the discrimation value as follows:

i.           Facilitation Value: The facilitation value of a test item identifies the question “as how easy is the test item”. The score obtained by the upper 30% students and marks obtained by the lower 30% students are summed and divided by the total marks in a test item. The formula thus is :

FV= (RU + RL)(2xN*marks of test item)

Where N= no. of students in a group. RU = sum of marks obtained by upper group

RL = sum of marks obtained by lower group

When FV=1 means that all students in lower group and all students in upper group answered the test item. So it can be so assumed that the test item was very easy.

 When FV=0, means nobody answered the question, it means that either the question was so tough that no one was able to answer the question or else there was a problem in understanding the topic by the students which further mean that there might be problem in teaching learning methodology adopted by the faculty.

ii.                  Discrimination Index: Discrimination value is used in used to discriminate among good and the bad students. This value also indicates how good the test item was in deciding among the good and the bad students.  The formula for finding the decimation value is:

DI = (RU – RL) / (N*marks of the test item)

DI=1 when only the upper group answered the question, indicates that the question is tough and only good students can answer it.  DI=0 means both the bright and weak student have answered the question and is not able to discriminate among good and weak students.

 Conclusion: If applied properly, the level or the quality of the test items can be evaluated for its effectiveness in discriminating the good and the weak students.