Validity of Instrument Try- out Findings

Table 4.1. The Table of Students’ score in Validity Computation No. Code X Y X 2 Y 2 XY 1 T-15 1 37 1 1369 37 2 T-21 1 37 1 1369 37 3 T-12 1 35 1 1225 35 4 T-19 1 35 1 1225 35 5 T-4 1 35 1 1225 35 6 T-26 1 35 1 1225 35 7 T-25 1 34 1 1156 34 8 T-23 1 31 1 961 31 9 T-22 1 28 1 784 28 10 T-2 1 28 1 784 28 11 T-16 0 28 784 12 T-7 1 28 1 784 28 13 T-17 1 26 1 676 26 14 T-18 0 26 676 15 T-9 0 26 676 16 T-3 0 25 625 17 T-20 1 25 1 625 25 18 T-10 1 23 1 529 23 19 T-11 0 22 484 20 T-28 1 20 1 400 20 21 T-6 0 20 400 22 T-8 0 19 361 23 T-14 1 16 1 256 16 24 T-13 1 16 1 256 16 25 T-5 0 15 225 26 T-24 0 12 144 27 T-1 1 13 1 169 13 28 T-27 0 12 144 Σ 18 707 18 19537 502 r xy = { } { } ∑ ∑ ∑ ∑ ∑ ∑ ∑ − − − − 2 2 2 2 y y N x x N y x xy N r xy = } } { { 2 2 707 19537 28 18 18 28 707 18 502 28 − × − × − r xy = 499849 547036 324 504 12726 14056 − − − r xy = 47187 180 1330 × r xy = 8493660 1330 r xy = 388 , 2914 1330 r xy =0,456 From the computation above, the result of computing validity of the item number 1 was 0,456. After that the writer consulted the result to the table of r product moment with the number of subjects N = 28 and significance level 5 it was 0,374. Since the result of the computation was higher than r in the table, the index of validity of the item number 1 was considered to be valid. The list of the validity f each item could be seen in appendix 3.

4.1.2 Reliability of instrument

A good test must be valid and reliable. Besides the index of validity, the writer calculated the reliability of the test using Kuder- Richarson formula 20 K-R 20. The computation of the reliability of the test was based on the data in appendix 3. Before computing the reliability, the writer had to compute varian S 2 = standard deviation first with the formula below: S 2 = N N y y ∑ ∑ − 2 2 S 2 = 28 28 707 19537 2 − S 2 = 28 75 . 17851 19537 − S 2 = 28 25 . 1685 S 2 =60.1875 The computation of the varian S 2 was 60.1875. After finding the varian S 2 the writer could compute the reliability of the test as follows: r 11 = ⎟⎟⎠ ⎞ ⎜⎜⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ∑ 2 2 1 s pq s n n r 11 = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − 1875 . 60 392 . 8 1875 . 60 1 40 40 r 11 =1.0265 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ 1875 . 60 7955 . 51 r 11 =1.0265 8606 . × r 11 =0.8826 From the computation above, it was found out that r 11 the total of reliability test was 0.882, whereas the number of subjects were 28 and the critical value for r- table with significance level 5 was 0,374. Thus the value resulted from the computation was higher than its critical value, it could be concluded that the instrument used in this research was reliable.