Reliability Instruments and Data Gathering Technique

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1.4.1.4 Criterion Validity

Criterion validity refers to the relationship between scores obtained using the instrument and scores obtained using one or more other instruments or measures Fraenkel Wallen, 1993.

1.4.2 Reliability

After fulfilling the validity of the test, the researcher found out the test reliability. Fraenkel Wallen state that reliability is the consistency of the scores obtained. In the test, the researcher gave some questions about passive voice to be answered by the respondents. The test was used to measure the students’ mastery on form and function. Therefore, the students should be able to understand the form of passive voice to master it. In brief, after designing the test, the researcher administered the test to the students of ELESP 20112012 academic year in Sanata Dharma University. To sum up, in answering the questions, the respondents should be able to understand the function of subject and object in a sentence. By doing so, they would not be confused in making an active or passive sentence. There are three methods that can be used to measure the reliability of the test: test-retest method, equivalent-forms method, and internal consistency method. In this research, the researcher used split-half procedure which is included in consistency method. 29 The split-half procedure involves scoring two halves usually odd items versus even items of a test separately for each person and then calculating a correlation coefficient for the two sets of scores Fraenkel Wallen, 1993. After the results were collected, the items in the test were divided into two comparable halves, the first half was the odd-numbered items X and the second half was even-numbered items Y. The students’ scores on each half were then counted. To determine the correlation between the two set of scores, the writer used Pearson Product Moment. The formula is as follow: rxy = ∑ X – Mx Y – My NSxSy Where: rxy = Pearson product-moment correlation efficient X = each students’ score on Test X Mx = mean on Test X Sx = standard deviation on Test Y Y = each students’ score on Test Y My = mean on Test Y Sy = standard deviation on Test Y N = the number of students who took the two sets This computation was the reliability of the half test. To determine the reliability of the full test, the writer employed the Spearman-Brown prophecy formula. The formula is: 30 Reliability of scores = 2 x reliability for ½ test on total test 1+ reliability for ½ test Best in his book Research in Education 1983 interprets the coefficient in several criteria: Coefficient r Relationship .00 – .20 negligible .20 - .40 Low .40 - .60 moderate .60 - .80 Substantial .80 – 1.00 High to very high The table above presented the interpretation of the reliability coefficient of the test which was based on Best’s book. The range of each criterion is 0.20. If the coefficient is only 0.20 - 0.40, the test is not reliable or has a minimum reliability. In other words, the test should be revised. If the coefficient is between the ranges 0.20 – 0.40, the reliability is still low which means that the test needs to be revised. Meanwhile, if the test reliability coefficient achieves 0.40 – 0.60, it means the test is moderate. In other words, the test is acceptable, yet it still needs revision. A good test may have a reliability coefficient between the ranges 0.60 – 0.80. The test with that coefficient was already reliable, yet the test with 0.80 – 1.00 as the reliability is better. The last two criteria do not need any significant revision. The data gathering procedure was conducted in Structure classes of the second semester students 20112012 academic year. The students were asked to do the thirty items in 45 minutes. The test was administered on April 18, 2012. After they had finished the test, the results were collected. 31

1.5 Data Analysis Technique

Before scoring the students’ test, the writer selected the sample using the Cluster Sampling Technique. There were 80 respondents in this research. The writer counted the correct numbers of the students’ work. To measure the students’ mastery on the use of passive voice, the writer performed statistical computation. The writer also found out the students’ difficulties in doing the test. Next, the writer tried to identify the possible causes of the students’ difficulties based on the test result and also the theories on Chapter II.

1.6 Research Procedure

The writer selected the sample using the Cluster Sampling Technique. There were 80 students who were considered the representative samples of the population. After that, the researcher conducted the test. The writer scored the students’ work in which the standard used to determine whether the answer is correct or incorrect was the authoritative English grammar textbooks and also on the review of the literature. Then the writer counted the students’ correct answers in the whole test and also in each part of the test. Based on the findings, the writer found out the percentage of correct answers. To know the students’ mastery on the use of passive voice in each tense, the writer performed necessary statistical computation. The result of computation as then compared to the minimum standard of mastery stated in the Peraturan Akademik Universitas Sanata Dharma 1998. The students’ mastery