Concept of Validity Types of Validity
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1. Increasing the sample of material select for testing. The larger the sample,
the greater the probability that the test as a whole is reliable 2.
Administration and scoring of the test. It is suggested to make a rating scale. So that the maker can identify precisely what he or she expects for
each scale and assign the most appropriate grade to the task being assessed.
There are some methods that can be established in computing reliability according to Henning 1987:81: they are 1 Test-Retest, 2 Parallel Forms, 3 Inter-
Rater, 4 Split Half, and 5 Kuder Richardson KR-20 and KR-21. In this research, the writer assessed the reliability of the test by using formulation Kuder
Richardson 21. But firstly, the writer calculated the total scores divided by the number of subject to obtain the mean. The writer used standard deviation. The
purpose of obtaining the standard deviation is to measure the standard from the mean. It means that how get the individual data in a data set was dispersed from
the mean. The formula of standard deviation according to Henning 1987:40 is:
S =
√
∑
Where, S : the standard deviation
X : the student’s score
x : the mean of value N : the number of students
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After getting the standard deviation, then the writer used kuder richardson 21 formula Henning, 1987:84 to determine the reliability of the whole test as
follow:
RtKR21=
Where, N
: the number of items in the test x
: the mean of the test scores S²
: the variance of the test scores Rt
: reliability Tuckman 1995:256 states that the reliability of a test can vary between 0.00 and
1.00. A reliability of 0.00 indicates that a test has no reliability and hence is an inadequate test for making any judgement about the students. A reliability of 1.00
is a perfect reliability, indicating a perfect or error-free test. Reliability here is reported with numbers between 0.00 and 1.00. For computing the reliability of the
test, the writer utilized kuder richardson 21, since it was simple enough. It just required three types of information, they were, the number of items, mean, and
standard deviation of a test. And the correlation of coefficient would be interpreted by using the following criteria:
0.90 – 1.00 : High
0.50 – 0.89 : Moderate
0.00 - 0.49 : Low
Hatch and Farhady: 1982:247