CHAPTER III RESEARCH METHOD
E. Research Instrument
2. Instrument Calibration
√
(∑x2)( ∑y2)The writer use the correlation formula that was proposed by Pearson known as the product moment, as follow:
rxy = ∑xy
Explanation:
= Index correlation ‘r’ product moment = Number of Cases
= Total score = Total score
= Total the multiplication between score dan .
To measure the students’ writing motivation, the writer used questionnaire. The total item of questionnaire is 20 items with three alternative answers, as follows:
1) Alternative answer A is given by score 3 2) Alternative answer B is given by score 2 3) Alternative answer C is given by score 1
A set of questionnaire was given in order to know the students’
extrinsic motivation toward the descriptive writing ability. The result of the questionnaire as follow:
1) Validity of Questionnaire Items about Students’ Extrinsic Motivation
Table 7
The Result of Questionnaire Items Validity of the Students’ Extrinsic Motivation at the Seventh Grade of MTs Ma’arif Nu 5 Sekampung
No Students’
Name
Item Number Total
Score 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1 AS 3 3 3 3 3 2 3 2 2 3 2 3 2 3 3 3 2 3 2 2 52
2 AC 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
3 CT 3 3 3 3 2 2 3 2 2 2 2 3 2 3 3 2 2 3 2 2 49
4 DA 3 3 3 3 3 3 3 2 3 3 3 3 3 3 3 3 3 3 2 3 58
5 HS 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
6 HK 3 3 3 3 2 2 3 3 2 2 2 3 2 3 3 2 2 3 3 2 51
7 KN 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 3 3 3 3 3 59
8 LA 2 2 2 2 2 3 2 3 3 2 3 2 3 2 3 2 3 2 3 3 49
9 LN 3 2 2 2 2 2 2 2 2 2 2 3 2 2 2 2 2 2 2 2 42
10 MS 2 2 2 2 1 2 2 2 2 1 2 2 2 2 3 2 2 2 2 2 39
11 MA 3 3 2 2 2 2 2 2 2 2 2 3 2 3 2 2 2 2 2 2 44
12 MH 3 3 3 2 3 3 2 3 3 3 3 3 3 3 2 3 3 2 3 3 56
13 NI 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 40
14 NS 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 40
15 NR 2 3 3 3 3 2 3 2 2 3 2 2 2 3 3 3 2 3 2 2 50
16 ND 3 3 3 3 3 2 3 3 2 3 2 3 2 3 3 3 2 3 3 2 54
17 RA 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
18 RE 3 3 3 3 2 3 3 2 3 2 3 3 3 3 3 2 3 3 2 3 55
19 RA 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
20 RW 3 3 3 3 1 3 3 3 3 1 3 3 3 3 3 1 3 3 3 3 54
21 RG 3 3 3 3 3 2 3 2 2 3 2 3 2 3 3 3 2 3 2 2 52
22 RY 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
23 RP 3 3 3 3 2 2 3 2 2 2 2 3 2 3 3 2 2 3 2 2 49
24 SA 3 3 3 3 3 3 3 2 3 3 3 3 3 3 3 3 3 3 2 3 58
25 SK 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 60
26 SW 3 3 3 3 2 2 3 3 2 2 2 3 2 3 3 2 2 3 3 2 51
27 TA 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 3 3 3 3 3 59
28 TP 2 2 2 2 2 3 2 3 3 2 3 2 3 2 3 2 3 2 3 3 49
29 WD 3 2 2 2 2 2 2 2 2 2 2 3 2 2 2 2 2 2 2 2 42
Total Score 81 80 79 78 71 73 78 73 73 71 73 81 73 80 79 72 73 78 73 73 1512 Source: The Result of Questionnaire of the Students’ Extrinsic Motivation at the Seventh Grade of MTs Ma’arif NU 5 Sekampung
√(∑x2)( ∑y2)
√(80) (27437)
√ 2194960
1481,53 Question Item Number 1
Table 8
The Calculation of Product Moment for number 1
Respondents X Y X2 Y2 XY
1 3 52 9 2704 156
2 3 60 9 3600 180
3 3 49 9 2401 147
4 3 58 9 3364 174
5 3 60 9 3600 180
6 3 51 9 2601 153
7 3 59 9 3481 177
8 2 49 4 2401 98
9 3 42 9 1764 126
10 2 39 4 1521 78
Jumlah 28 519 80 27437 1469
rxy = ∑xy
= 1469
= 1469
= 1469
= 0,9915
= 0,991
√(∑x2)( ∑y2)
√(75) (27437)
√ 2057775
1434,49 Question Item Number 2
Tabel 9
The Calculation of Product Moment for number 2
Respondents X Y X2 Y2 XY
1 3 52 9 2704 156
2 3 60 9 3600 180
3 3 49 9 2401 147
4 3 58 9 3364 174
5 3 60 9 3600 180
6 3 51 9 2601 153
7 3 59 9 3481 177
8 2 49 4 2401 98
9 2 42 4 1764 84
10 2 39 4 1521 78
Jumlah 27 519 75 27437 1427
rxy = ∑xy
= 1427
= 1427
= 1469
= 1, 02405733
= 1,024
1. Question number 1 : 0,991 2. Question number 2 : 1,024 3. Question number 3 : 0,994 4. Question number 4 : 0,994 5. Question number 5 : 0,987 6. Question number 6 : 0,991 7. Question number 7 : 0,994 8. Question number 8 : 0,991 9. Question number 9 : 0,987 10. Question number 10 : 0,987 11. Question number 11 : 0,991 12. Question number 12 : 0,991 13. Question number 13 : 0,991 14. Question number 14 : 0,994 15. Question number 15 : 0,982 16. Question number 16 : 0,993 17. Question number 17 : 0,991 18. Question number 18 : 0,994 19. Question number 19 : 0,986 20. Question number 20 : 0,991
To know the valid and invalid items, by seeing the correlation value on column of index of all items correlation then compared with interpretation table of r observed below:
Table 10
Interpretation table of r observed
Value of “r observed” Interpretation
0.800 – 1,00 Very High
0,600 – 0, 800 High
0,400 – 0,600 Fair
0,200 – 0,400 Low
0,000 – 0.200 Very low
Table 11
Interpretation of Validity
Question Items Critical Value Interpretation Explanation
1 0,991 Valid Very High
2 1,024 Valid Very High
3 0,994 Valid Very High
4 0,994 Valid Very High
5 0,987 Valid Very High
6 0,991 Valid Very High
7 0,994 Valid Very High
8 0,991 Valid Very High
9 0,987 Valid Very High
10 0,987 Valid Very High
11 0,991 Valid Very High
12 0,991 Valid Very High
13 0,991 Valid Very High
14 0,994 Valid Very High
15 0,982 Valid Very High
16 0,993 Valid Very High
17 0,991 Valid Very High
18 0,994 Valid Very High
19 0,986 Valid Very High
20 0,991 Valid Very High
Based on the explanantion above, it can be concluded that the instruments (question number 1 until 20) are valid.
b. Reliability
Reliability of a measuring instrument is the degree of consistency with which in measures whatever it is measuring. This quality is essential in any kind of measurement.42
The way to find the reliability coefficient is to find a correlation between odd item score and even item score, by using the Pearson product moment correlation formula. Then, the calculation only shows the difference, not showing reliability. To find out the level of reliability, it will be used the formula of Spearman Brown technique, as follow:
r11 =
12 12
12 12
1 2
r r +
×
Keterangan :
r11 : Adjusted reliability coefficient
12 12
r : Correlation between half test scores
After getting the result, then it will be consulted with the criteria:
0,800 – 1,00 : Very high 0,600 – 0,800 : High 0,400 – 0,600 : Fair 0,200 – 0,400 : Low 0,000 – 0,200 : Very low.
42Ibid, p.236
1) Reliability of Students’ Extrinsic Motivation Questionnaire Table 12
List of Total Score Odd Items
Rspdn Score Odd Items Total
1 3 5 7 9 11 13 15 17 19 (X)
1 3 3 3 3 2 2 2 3 2 2 25
2 3 3 3 3 3 3 3 3 3 3 30
3 3 3 2 3 2 2 2 3 2 2 24
4 3 3 3 3 3 3 3 3 3 2 29
5 3 3 3 3 3 3 3 3 3 3 30
6 3 3 2 3 2 2 2 3 2 3 25
7 3 3 3 3 3 3 3 2 3 3 29
8 2 2 2 2 3 3 3 3 3 3 26
9 3 2 2 2 2 2 2 2 2 2 21
10 2 2 1 2 2 2 2 3 2 2 20
Table 13
List of Total Score Even Items
Rspdn Score Even Items Total
2 4 6 8 10 12 14 16 18 20 (Y)
1 3 3 2 2 3 3 3 3 3 2 27
2 3 3 3 3 3 3 3 3 3 3 30
3 3 3 2 2 2 3 3 2 3 2 25
4 3 3 3 2 3 3 3 3 3 3 29
5 3 3 3 3 3 3 3 3 3 3 30
6 3 3 2 3 2 3 3 2 3 2 26
7 3 3 3 3 3 3 3 3 3 3 30
8 2 2 3 3 2 2 2 2 2 3 23
9 2 2 2 2 2 3 2 2 2 2 21
10 2 2 2 2 1 2 2 2 2 2 19
After getting odd and even score, then it can be included into table, as folow:
√(∑x2)( ∑y2)
√(6825)( 6902)
√ 47106150
Table 14
Reliability Test of Odd and Even Score Questionnaire
Rspdn X Y X2 Y2 XY
1 25 27 625 729 675
2 30 30 900 900 900
3 24 25 576 625 600
4 29 29 841 841 841
5 30 30 900 900 900
6 25 26 625 676 650
7 29 30 841 900 870
8 26 23 676 529 598
9 21 21 441 441 441
10 20 19 400 361 380
Jumlah 259 260 6825 6902 6855
rxy = ∑xy
= 6855
= 6855
= 6855 6868,392 = 0,9980501
= 0,998
Based on the calculation above, the result included into spearman brown formula, as follow:
r11 =
12 12
12 12
1 2
r r +
×
= 2 x 0,998 1+0,998
= 1,996 1,998
= 0,998
The result of r11 is 0,998. It is included into criteria 0,800 – 1,00.
and it is included into very high category. It shows that the questionnaire about extrinsic motivation to descriptive writing ability is feasible to used.
Based on the Jacobs’s scoring profile that individual writing score can be evaluated by counting up the scale from each writing aspect, such as content, organization, vocabulary, language use, and mechanics. The writing scoring profile is presented as scoring rubric as follow:43
Table 15
The writing scoring rubric by Jacobs et.al
Aspects Score Performance Description Weighting Content
(C) 30%
-Topic -Details
4 The topic is complete and clear and the details are relating to the topic.
3 x 3 The topic is complete and clear but the
details are almost relating to the topic.
2 The topic is complete and clear but the details are not relating to the topic.
1 The topic is not clear and the details are not relating to the topic.
Organization 4 Identification is complete and 2 x
43 Weigle. S. Cushing, Assessing Writing, (Cambridge: Cambridge University Press, 2002), p.116
(O) 20%
-Identification -Description
descriptions are arranged with proper connectives.
3
Identification is almost is complete and descriptions are arranged with almost proper connectives.
2
Identification is not complete and descriptions are arranged with few misuse of connectives.
1
Identification is not complete and descriptions are arranged with misuse of connectives.
Grammar (G) 20%
-Use Present Tense -Agreement
4 Very few grammatical is not complete or agreement inaccuracies
2 x 3 Few grammatical or agreement
inaccuracies but not effect on meaning.
2 Numerous grammatical or agreement inaccuracies.
1 Frequent grammatical or agreement inaccuracies.
Vocabulary (V) 15%
4 Effective choice of words and word forms.
1,5 x 3 Few misuse of vocabularies, word forms,
but not change the meaning.
2 Limited range confusing words and word forms.
1 Very poor knowledge of words, word forms, and not understandable.
Mechanics (M) 15%
-spelling -Punctuation -Capitalization
4 It uses correct spelling, punctuation, and capitalization.
1,5 x 3 It has occasional errors of spelling,
punctuation, and capitalization.
2 It has frequent errors of spelling, punctuation, and capitalization.
1 It is dominated by errors of spelling, punctuation, and capitalization.
Score = 3𝐶𝐶+2𝑂𝑂+2𝐺𝐺+1,5𝑉𝑉+1,5𝑀𝑀
40 x 10