L = the number of pupils in the lower group who answered the item correctly N = number of pupils in each of the groups.
49
The classifications of the index of discriminating power D are: DI = 0.07
– 1.00 = Excellent 0.40
– 0.70 = Good 0.20
– 0.40 = Satisfactory ≤ 0.20 = Poor
Negative value on D = Very Poor.
50
By using the formula of DP and the criteria above, teachers can select the items which are fulfilled to that standardizations or not, so hehe can determine
to use, revise or skip the item for the future. In this skripsi, the writer is focusing on testing procedure. Acoording to
explanation above, there are two kinds of achievement tests which are held periodically, they are progress and the final test.
49
Surapranata, op. cit., p. 31.
50
Ibid., p. 389.
28
CHAPTER III RESEARCH METHODOLOGY
A. Place and Time of the Research
The research was conducted at “SMP Al Wathoniyah 09” East Jakarta. This is located at JL. Raya Penggilingan No. 99 Cakung, East of Jakarta. The summative
test was held on June 10, 2014. The writer did the research in June, 9
th
2015. The writer took the English summative test papers and the students’ score of second
grade period of 20142015 to be analyzed.
B. Technique of Sample Taking
The writer took the sample from students of “SMP Al Wathoniyah 09 East Jakarta
”. The total number of second year students was 146 students; those were divided into 3 classes. The writer used technique systematical sampling random.
The sample was chosen based on certain sequences by using ordinal.
1
In determining the sample the writer used multiplied by 3 in all classes. So the
sample of this research was 49 students. After that the writer divided the students into three groups; they were upper group, middle group and lower group. Next the
writer took upper and lower group only to be analyzed.
C. Technique of Data Collecting
To collect the data that relate to the topic of discussion, the writer took the summative test from SMP Al Wathoniyah 09 East Jakarta in order to analyze the
discriminating power and to categorize discriminating power as excellent, good, satisfactory, poor, and very poor in every item.
1
Husaini Usman, Pengantar Statistika, Jakarta: PT. Bumi Aksara, 2006, p. 185.
29
D. Research Instrument
a. Students’ score of the English summative test in which the English teacher
made. b.
English summative test of the second year students of “SMP Al Wathoniyah
09 East Jakarta” academic year 20132014.
E. Technique of Data Analysis
In this research, the writer used quantitative method to analyze the discriminating power of
English summative test items of second year of “SMP Al Wathoniyah
09 East Jakarta” quantitative method means the investigation relies on statistical analysis mathematical analysis of the data which is typically in
numeric form.
2
And to analyze the discriminating power the writer used a statistic formula, namely, the discriminating power index:
DP = Correct U
– Correct L n
Explanation: DP: Discriminating Power
U : Sum of the students from the upper group who answered correctly L : Sum of the students from the lower group who answered correctly
N : Number of the candidates in one group.
The classifications of the index of discriminating power D are: DI
= 0.70
– 1.00 = Excellent
0.40 – 0.70
= Good 0.20
– 0.40 = Satisfactory
≤ 0.20 = Poor
Negative value on D = Very Poor.
3
2
John W. Creswell, Educational Research: Planning, Conducting, and Evaluating Quantitative and Qualitative Research, Boston: Pearson Education. Inc., 2012, 4
th
edition, p. 15.
3
Anas Sudijono, Pengantar Evaluasi Pendidikan, Jakarta: PT. RajaGrafindo Persada, 2011, p. 389.
30
CHAPTER IV RESEARCH FINDINGS
A. Description of Data
The data which is used by the writer is the English summative test in the second grade of “SMP Al Wathoniyah 09” East Jakarta. This English
summative test was held on Tuesday, June 10
th
2014, that must be finished in 120 minutes. The total numbers of test items are 50 questions, which all of
them are multiple choices. The total numbers of students that took part in this analysis are 48
students. Anas Sudijono
in the book “Pengantar Evaluasi Pendidikan” demonstrated that the selection of criterion groups
“based upon the upper 27 percent and lower 27 percent of the provided by the greatest confidence that the upper
group is superior in the trait measured by the test as compared to the lower group.
”
1
The middle 46 percent of the papers is not used when 27 percent in the upper and 27 percent in the lower groups are employed in item analysis.
Based on the statement, the writer classified the students into three groups; upper, middle and lower group. The writer took only 27 of the lower group
and 27 of the upper group for this analysis. And the rest students that belong to the middle group will not take part to this analysis. The next table is
the students’ scores and group position in English summative test.
1
Anas Sudijono, Pengantar Evaluasi Pendidikan, Jakarta: PT. RajaGrafindo Persada, 2011, p. 387.
