1. CHAPTER 11I
METHOD OF INVESTIGATION
1. Data Collection
1.1 Test
Test is a number of questions that used to measure personality,
intelligence, attitude and achievement someone. In this research, the
researcher will give pre-test and post-test. Pre-test will be given at the
beginning of research to both control and experiment class (similar
question that related to the topic) while post-test will be given to
experiment class because it is the point that researcher can compare the
differences result of the test between control and experiment class.
2.1 Population
Population is all of the research subject1
. In this research, the researcher
will take population of eight grade students of SMP NU 05 Awwalul
Hidayah Gemuh kab. Kendal in the academic year of 2009/2010 which has
two classes (VIII A and VIII B) and each class consist of 43 students.
3.1 Sample
Sample is a part of population to be researched2
. Sample is a subset of
individuals from a given population3
. Sample must be reflective with the
true example in the field. In this case, the researcher will take sample from
eight grade students of SMP NU 05 Awwalul Hidayah Gemuh kab.
Kendal in the academic year of 2009/2010 which has two classes (VIII A
as an experiment class and B as a control class).
1
Suharsimi Arikunto. Prosedur Penelitian: suatu pendekatan praktek. (Jakarta: Rineka
Cipta, 2006), p. 130.
2
Ibid, p. 131.
3
David Nunan. Research Methods in Language Learning. (New York: Cambridge
University Press, 1992), p. 27.
22

2. 4.1 Variable
To answer the research problems, there are some variables that the
researcher wants to investigate. The variables are as follow:
a. Independent Variable (X)
Independent variables are the conditions or characteristics that are
manipulated by the researcher in order to explain the relation with
the observed phenomena4
. The independent variable of this study,
according to the definition above is the using of mind-mapping to
improve students’ understanding on modal.
b. Dependent Variable (Y)
Dependent variables are the conditions or characteristics that
appear, disappear, or change as the researcher introduces, removes,
or changes independent variables5
. Referring to the definition, the
dependent variable of the study is the improvement of students’
understanding on modal.
5.1 Observation
Observation is an activity to observe something by using sense toward a
particular object. In this research, the researcher will observe of school,
students and English teacher of the school. In this research the writer will
use check list (√) to get the data. The observation is used to know the
activities during teaching and learning process, such as how teacher is
explains the material, what is the students’ respond and how is the
student’s work in doing the test.
4
Narbuko and Achmadi, Metodologi Penelitian, (Jakarta: Bumi Aksara, 2004), p. 119.
5
J. W. Best, Research in Education, (New Jersey: Prentice Hell, 1981), p. 60.
23

3. Table 1
Observation Scheme
No. Activities Check list Grade
1 2 3 4 5
A. Teacher preparation of lesson
• Specification of aims
• Choice of appropriate material
• Choice of appropriate teaching aids
B. Teacher organization of the lesson and
the class
• Introduction or explanation of
material
• Manage the classroom
• Motivate students
C. Students’ activities
• Students’ participation toward
teacher’s explanation
• Students are active during learning
and teaching process
• Students’ work communication
during in a group work
• Students’ seriousness in
understanding the material
• Students are active in answering the
teacher’s question
In which, percentage
1 : poor 0 %-35 %
2 : fair 40 %-59%
3 : average 60 %-74 %
4 : good 75 %-84 %
5 : excellent 85 %-100 %
2. Focus of The Research
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4. This research is experimental study. An experiment is defined as a situation in
which one observes the relationship between two variables by deliberately
producing a change in one and looking to see whether this alteration produces
a change in the other6
. In research, the writer will use experiment to teach
class (VIII A) by using mind-mapping to improve students’ understanding on
modal and control class (VIII B) without using mind-mapping.
3. Participant and Setting
The participants that used by the researcher are the students on eight grade at
SMP NU 05 Awwalul Hidayah Gemuh Kendal. There were 118 students, VIII
A (59 students) and VIII B (59 students).
4. Instrument of The Study
The writer used one test type only. It was multiple choice completions. This
type of test was chosen because of the following advantages:
a. The technique of scoring is easy.
b. It was easy to compute and determine the reliability of the test.
c. It was more practical for the students to answer.
4.1 Try Out
The quality of the data, whether it is good or bad, is based on the
instrument used. A good instrument fulfills two important qualifications,
such as reliability and validity. So, before the test was used an instrument
to collect the data, it had been tried out first to the students in another
class. After the result of the try out was gained, the analysis was made to
find out the validity and reliability of the items of the test. Some items
remained to be used while some others were left out.
4.2 Validity of the Test
6
James Dean Brown and Thedore S. Rodgers, Doing Second Language Research, (New
York: Oxford University Press, 2002), p. 211.
25

5. Validity shows whether an instrument is valid. In this study, the validity of
each item is calculated using the product moment formula7
:
( )( )
( ){ } ( ){ }2222
yyxx
yxxy
rXY
ΣΝΣΣΝΣ
ΣΣ−ΝΣ
=
−−
In which,
r XY = coefficient of correlation between x and y variable or
validity of each item
N = the number of students / subject participating in the test
Σ X = the sum of score in each item
Σ X
2
= the sum of square score in each item
Σ y= the sum of the total score from each student
Σ y
2
= the sum of the square score from each student
Σ XY = the sum of multiple score from each students with the total
score in each item
4.3 Reliability of the Test
Reliability shows whether an instrument is reliable and can be used as a
device to collect the data with the stability of t-set score. The formula
which is used is the split half spearman-brown. In this case, the writer split
the formula is as follows:
( )2/21/1
2/21/2
1
1
11
r
r
r
+
×
=
In which,
11r = the reliability of the instrument
2/21/1r = xyr the correlation index of the odd and even
The r XY was resulted from this following formula:
7
Suharsimi Arikunto, Dasar-dasar Evaluasi Pendidikan, (Jakarta: PT. Bumi Aksara, 2002),
p. 72.
26

6. r XY =
( )( )
( ){ } ( ){ }2222
∑ ∑∑∑
∑∑ ∑
−Ν−Ν
−Ν
yyxx
yxxy
In which,
r XY = coefficient of correlation between x and y variable
N = the number of students/subject participating in the test
Σ X = the sum of odd item
Σ X
2
= the sum of the square score of the odd item
Σ y = the sum of item
Σ
2
y = the sum of the square score of the even items
Σ xy = the sum of multiple of score from odd and even
4.4 Degree of Test Difficulty
After try out was conducted, each item is classified in the difficulty level
by using this formula:
JS
B
P =
In which,
P = item difficulty
B = number of students who answered the item correctly
JS = number of students
The level of difficulty of each item was determined by using this following
categorization:
0 < P ≤ 0.3 is difficult
0. 3 < P ≤ 0. 70 is medium
0. 7 < P ≤ 1 is easy
4.5 Discriminating Power
27

7. The discriminating power measures how well the test items arranged to
identify the differences in the students’ competence. The formula is8
:
JB
BB
JA
BA
D −=
In which,
D = number of students in the upper group who answered the item
correctly
BA = number of students in the lower group who answered in the item
correctly
JA = number of all students in the upper group
JB = number of all students in the lower group
The criteria are:
D ≤ 0.2 is poor
0. 2 < D ≤ 0. 4 is fair
0. 4 < D ≤ 0. 7 is good
0. 7 < D ≤ 1 is very good
4.6 Homogeneity Test
Homogeneity test is used to compare variants in a group of three
categories data or more and its categories can be compared fairly if
each category is homogeneity.
The formula as follows:
lowestVar
higestVar
F
.
.
max =
( ) ( )
( )1
22
2
−Ν
ΝΧ−
=
∑ ∑X
SDVarian
4.7 Normality Test
It is used to know the normality of the data that is going to be analyzed
whether both groups have normal distribution or not. To find out the
8
Ibid, p. 213.
28

8. distribution data is done normality test with the Chi-square. Step by
step Chi-square test is as follows:
1) Determine the range (R); the largest data reduced the
smallest.
2) Determine the many class interval (K) with formula:
K = 1+ (3,3) log n
3) Determine the length of the class, using the formula:
P = assnumberofcl
rangeR
4) Make a frequency distribution table
5) Determines the class boundaries (bc) of each class
interval
6) Calculating the average Xi ( X ), with the formula:
X =
∑
∑
i
ii
f
xf
7) Calculate variants, with the formula:
1
)( 2
−
−
=
∑
n
xxf
S
ii
8) Calculate the value of Z, with the formula:
Z =
s
xx −
x = limit class
x = Average
S = Standard deviation
9) Define the wide area of each interval
10) Calculate the frequency expository (Ei), with formula:
Ei = n x wide area with the n number of sample
11) Make a list of the frequency of observation (Oi), with the
frequency expository as follows:
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9. class bc Z P L Ei
Ei
EiOi −
12) Calculate the chi-square ( 2
X ), with the formula:
( )
∑=
−
=
k
i i
ii
E
EO
X
1
2
2
13) Determine the degree of validity (dk). In the calculation
of this data is arranged in list of frequency distribution consisting of
k pieces so that the interval to determine the criteria test used
formula dk = k-3, where k is the number of class intervals and α =
5%
14) Determining the value of 2
X table
15) Determining the distribution normality with test criteria:
If countX 2
> tableX 2
so the data is not normal distribution and
the other way if the countX 2
< tableX 2
so the data is normal
distribution. 9
5. Method of Data Analysis
To see whether the differences of the students’ understanding in “modal”
between those who was taught using mind-mapping and these who was taught
without using mind-mapping is significant or not, the t- test formula is used.






+





−+
+
+
=
NyNxNyNx
SScSSe
McMe
t
11
2
In which,
t = t - value
Me = the mean of the control group
Mc = the meant of the control group
SSe = the deviation of the experimental group
9
Sujana, Metode Statistika, (Bandung: Tarsito, 1996), p. 273.
30

10. SSc = the deviation of the control group
Nx = the number of the students in control group
Ny = the number of the students in experimental group
31