33 3 Style
The passages should have various types and style. The passages should have chronologically with series of events.
4 Language The passages are not overloaded with extremely difficult lexical, difficult
items and complex syntactical structure. The writer used multiple choice tests. This type of test was chosen because
of some reasons. First, multiple choice items represent the essence of the materials. Second, it measures knowledge, comprehension, analysis and
evaluation. Finally, it is easy to correct and there is no subjectivity in scoring process.
3.5 Methods of Collecting Data
There are some steps to collect the data.
3.5.1 Try Out Test
The quality of the data whether it is good or bad is based on the instrument to collect data. A good instrument should fulfil some important qualifications. Those
are validity, reliability, difficulty level, and discriminating power. Therefore, before the test was used as an instrument to collect the data, it should be tried out
first to the students in other class beside the experimental class and control class.
34 The writer chose X MIPA 5 as the class to try the instrument out. The activity was
held on August, 31
st
2015. The data of try out was analyzed to determine whether or not the items were
valid and reliable. The invalid and unreliable items were not used. 3.5.1.1 Validity of the Test
“Test validity is defined as the degree to which a test measures what it claims to
be measuring ” Brown, 1988:101. It means that researchers must use test that tap
the variables of interest clearly as they used. To calculate the validity of each item the writer will use the product moment
formula:
=
Bachman, 2004:86 Tuckman, 1978:163
In which,
r
xy
:
correlationcoefficient between x and y variable N : number of test-takers
Σх : number of test items Σх
2
: quadrate of number of test items Σу : total score of test items
Σу
2
: quadrate of total score of test items Σху : multiplication of items score and total score
35 3.5.1.2 Reliability of the test
Reliability is one of the necessary requirements for test. The test could be said properly to be used when th
ey were reliable. “The reliability of a test is defined as the extent to which the results can be considered consistent or stable Brown,
1988:98 ”.
To measure the reliability of the test, the writer used SPSS with the
formula below:
= Where,
r
11
= the reliability of the instrument = the number of items.
= the means of the scores = the total of variance
To get the result of , the formula used is:
Where, N = the number of students participating in the test
Σу = the sum of even items Σу
2
= the sum of the square score of the even items
36 3.5.1.3 Difficulty level
After conducting and getting the result of the try out, the writer classified and selected the items by using this formula:
Brown, 2004:59
Where, IF
= Item Facility Level of difficulty B
= number of test-takers answering the item incorrectly JS
= number of test-takers responding to that item
Classifications of level difficulty of are: P = 0, 00
: test items are too difficult 0, 00 P ≤ 0, 30
: test items are difficult 0, 30 P ≤ 0, 70
: test items are medium 0, 70 P ≤ 1, 00
: test items are easy P = 1
: test items are too easy
3.5.1.4 Discriminating power
37 The discriminating power will measure how well the test items arranged to
identify the differences in the students‟ competence. The formula is:
-
Brown, 2004:59
Where, ID = Item Discrimination Discrimination Power
BA = number of top test takers that have correct answer BB = number of bottom test takers that have correct answer
JA = total participant of top test-takers JB = total participant of bottom test takers
3.5.2 Treatment
