3.3.1.3 Condition of the Test
3.3.1.3.1 Discriminating Power DP
The trial test was carried out on Monday, 13
th
October 2008. In the activity, 26 students were taken as the respondents to do the test consisted 100
multiple choice items. The items consisted of 100 TOEIC tests listening section. After finishing the test, the students’ result was collected to be scored. Based on
the result, an analysis was made to find out the discriminating power of each item. In order to find the discriminating power DP of each item, the writer will
select 50 of the upper group and 50 of the lower group. The Discriminating Power DP of an each item can be calculated by applying the following
procedure recommended by Heaton 1975: 174: 1 Arranged the student’s result in rank order of total score and divided them into
two groups of equal size i.e. a half of the top and the other half of the bottom.
2 Counted the number of the students in the upper and the lower group, who answered correctly.
3 Subtracted the number of the correct answers in the lower group from the number of the correct answer in the upper group.
4 Divided the difference by the number of he students in one group.
The procedure of calculating the DP can be expressed by the following formula:
H + L and H – L Where
H : number of highs who answer correctly
L : number of lows who answer correctly
H + L : total number who answer correctly success
H – L : How many more highs than lows answered correctly discrimination
Generally, the most appropriate and most effective are those who answered correctly by 60 to 70 percent of the class, but on classroom tests this
might range 30 to 90 percent. A figure under 30 percent indicates an item is probably too difficult; on over 90 percent that is too easy. Valette 1970:64
The Discriminating Power classification is as follows: 1
≤ D ≤ 0.20 = poor 2 0.20
≤ D ≤ 0.40 = sufficient 3 0.40
≤ D ≤ 0.70 = good 4 0.70
≤ D ≤ 1.00 = excellent If D is negative, all of the items are not good. So if all items which have
the D value are negative, it will be better to throw them away. The result of the computation of the discriminating power of the try out test can be seen in
Appendix.
3.3.1.3.2 Validity
Kategori