Technique of the Data ฀ollection

38 b. Categorization To make the categorization of the scores of students’ simple present and simple past tenses mastery, the ideal mean score Mi and the ideal standard deviation score SDi should be found first. The ideal mean score is 60 of the ideal maximum score, and the ideal standard deviation score is one fourth of the ideal mean score ฀urgiyantoro, 2001:401 There are twenty questions on the simple present and simple past tenses mastery. The results of the raw data of both groups the experimental and control groups are analyzed in the range of 60 - 100. The maximum score is 100 and the minimum score is 60. The Miwas 60 and the SDi was 15.The formula is presented in Table 4. Table 4: Formula of Data ฀ategorization Interval Scores Five Scales X ≥ Mi + 1,5 SDi Mi + 0,5 SDi ≤ X Mi + 1,5 SDi Mi – 0,5 SDi ≤ X Mi + 0,5 SDi Mi – 1,5 SDi ≤ X Mi – 0,5 SDi X Mi – 1,5 SDi Very Good Good Average Poor Very Poor 39 2. Inferential Statistics The inferential statistics is employed to make inferences about a population based on the data obtained from a sample. It is used to test the hypothesis whether there is significant difference in the simple present and simple past tenses mastery of the students who are taught using authentic materials and those who are not. The statistics used in this computation are test of normality, test of homogeneity, and test of hypothesis. a. ฀ormality Test The normality test is used to see whether or not the distribution of responses to the instrument is normal. In this case, the Chi-square test is used. It is gained from the scores of pre-test and post-test. To determine the level of significance, the researcher used Chi-square test in the significance level: 0.05 from SPSS version 16.0 of windows computer program. b. Homogeneity Test A homogeneity test is used to analyze whether the sample variance is homogeneous or whether the two groups are in the same condition. The analysis technique used to know whether the sample variance is homogeneous or not is the Levene’s test. In this study, the test of homogeneity was done using SPSS version of windows computer program. The test is considered homogeneous if the level of significance is more than 0.05. c. Hypothesis Test The hypothesis testing is used to see whether the hypothesis is right or not. To reveal the hypothesis which says ‘there is a significant difference in the simple 40 present and simple past tenses mastery of the students who are taught using authentic materials and those who are not’, the t-test is done in both groups.