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a. The Validity of the Instrument
The validity of the instrument is that it measures what it is supposed to measure. Fraenkel and Wallen 1993: 102 put forward that validity revolves
around the defensibility of the inferences researchers make from the data collected through the use of instrument. Linn and Gronlound 2000: 75 assert that validity
as follows: 1
Validity refers to the appropriateness of the interpretation of the results of an assessment procedure for a given group of individuals, not to the
procedure itself.
2 Validity is a matter of degree; it does not exist on an all-or-none basis.
Consequently, we should avoid thinking of assessment results as valid or invalid.
3 Validity is always specific to some particular use or interpretation. ….
Assessment results are never just valid; they have a different degree of validity for each particular interpretation to be made.
4 Validity is unitary concept. The conceptual nature of validity has
typically been described for the testing profession in a set of standards prepared by a joint committee made up of members from three
professional organizations that are especially concerned with educational and psychological testing and assessment. … Instead,
validity is viewed as a unitary concept based on various kinds of evidence.
5 Validity involves as overall evaluative judgment. It requires an
evaluation of the degree to which interpretations and uses of assessment results are justified by supporting evidence and in terms of
the consequences of those interpretations and uses.
The formula of validity for learning motivation questionnaire is as follows:
= ∑
ĸ
.
m ĸ
−
m
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Notes:
r
xy
: the coefficient of correlation between X and Y x
i
: score per items x
t
: the total score Besides, the reading test is an objective test. The Product Moment formula
is used to know the validity of the reading comprehension test:
1 1
2 2
q p
S r
n x
S
t t
i o
t
C -
C =
S =
If r
o
is higher than r
t
, the item is valid. From the validity testing, it is known that the number of valid items is 60
out of 90 items. It can be said that the 60 items can be used to collect the data. Besides, the number of learning motivation questionnaire is 30 items out of 50
items. In
Educational Research Quantitative and Qualitative Approach
, Christensen explains that content validity, criterion-related validity and construct
validity are three validities that can be used to measure the validity of the instrument 2000: 107. The writer uses construct validity to find out the validity
of the questionnaire. It refers to the extent to which the writer can infer some theoretical construct from the scores of a test. Moreover, Christensen defines that
construct validity involves formulating hypotheses about the expected behaviors that should occur from individuals who score high and low on a test and a
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tentative theory about why high and low scores should behave differently 2000: 110.
b. The Reliability of the Instrument.
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