CHAPTER 4 DISCUSSION OF FINDINGS
4.3 DISCUSSION OF PHASE 2 – IMPLIMENTATION OF THE INTERVENTION
4.4.1 Post-intervention learners quantitative data
4.4.1.6 Determining which mean differences are significant
However, although the ANOVA test can establish that there is a significant difference amongst the groups’ means, it is unable to determine which group(s) is/are
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significantly different form the other. Consequently, a post-hoc Least Significant Difference (LSD) test for multiple comparisons needed to be conducted to establish which of the mean differences between the three groups were in fact significant. A post hoc test is only conducted if the F value of the ANOVA is significant (Dornyei, 2007). The results of the LSD test are reported in Table 21.
Table 21: Results of LSD test
LSD test; variable vocabulary acquisition score; simultaneous confidence intervals
Cells 1st Mean 2nd Mean Mean Differ. Standard Error p value
{1}-{2} EG*pre EG*post -28.62 2.34 0.00 {1}-{3} EG*pre CA*pre 1.95 3.33 0.56 {1}-{4} EG*pre CA*post -12.73 3.33 0.00 {1}-{5} EG*pre CB*pre -3.68 3.64 0.32 {1}-{6} EG*pre CB*post -24.96 3.64 0.00 {2}-{3} EG*post CA*pre 30.57 3.33 0.00 {2}-{4} EG*post CA*post 15.89 3.33 0.00 {2}-{5} EG*post CB*pre 24.94 3.64 0.00 {2}-{6} EG*post CB*post 3.66 3.64 0.32 {3}-{4} CA*pre CA*post -14.68 2.38 0.00 {3}-{5} CA*pre CB*pre -5.63 3.67 0.13 {3}-{6} CA*pre CB*post -26.91 3.67 0.00 {4}-{5} CA*post CB*pre 9.05 3.67 0.02 {4}-{6} CA*post CB*post -12.23 3.67 0.00 {5}-{6} CB*pre CB*post -21.28 2.81 0.00
EG = Experiential Group; CA = Control Group A; CB = Control Group B.
Table 21 visually represents a comparison between the various pre- and post-test mean scores as well as the standard error and the p-values. The standard error of mean, displayed in Column 5, analyses the deviation within the different means and contains an estimation of how close the means of the various groups are to the mean of the entire population. If the standard error is small, the data are representative of
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the true mean, but if the standard error is large, the data may have some defects (Dornyei, 2007).
The scores that are of interest for the current study are the within-group comparisons of the pre- and post-test mean scores of each of the three groups. The cell numbers in Column 1 represent the different groups and either the pre- or post-test score. Cell 1, for instance, represents the Experimental Group’s pre-test score and Cell 2 = the Experimental Group’s post-test score. The mean difference of -28.62 reflected in Row 1, Column 3 is therefore the difference in the means of the pre- and post-test scores of the Experimental Group, a negative result indicating that the post-test score was higher than the pre-test score. The standard error for the Experimental Group is 2.34 and the p-value is p = 0.00. The standard error is relatively small and indicates that the mean is sufficiently close to the true mean of the total population, and the study sample can be regarded as sufficiently representative of the population.
The mean difference for Control Group A’s pre-and post-test scores is -14.68, with p = 0.00 and the standard error is 2.38. The results for Control Group B is -21.28 with the p value at p = 0.00 and a standard error of 2.81.
This within-group analysis shows that the difference in mean scores between the pre- and post-test scores of the Experimental Group (p = 0.00), Control Group A (p = 0.00) and Control Group B (p = 0.00) are all three statistically significant. In other words, within-group improvement in the form of vocabulary acquisition took place within each group during the intervention period. The biggest improvement from pre- intervention to post-intervention mean scores took place within the Experimental Group, followed by Control Group B. Control Group A displays the smallest mean improvement.
In addition to the within group comparisons, the comparison between the three groups’ post-test scores was also central to answering Research Question 1: whether explicit, interactive vocabulary instruction during L2 storybook reading impacts the vocabulary acquisition of Grade 1 learners. During the pre-intervention phase (refer 4.2.1) it was established that there was no significant difference in the p- values of the three groups, in other words the three groups were the same at the beginning of the research.
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The three rows reflecting the post-test comparisons are highlighted in Table 21 for ease of reference. The mean difference between the Experimental Group and Control Group A’s post-test scores is 15.89, p = 0.00 and the standard error = 3.33. The results for the analysis of the difference in mean post-test scores for the Experimental Group and Control Group B is 3.66 and p = 0.32, with a standard error of 3.64. The mean difference between Control Groups A and B is -12.23 with a p value of p = 0.00 and a standard error of 3.67. The multiple comparisons test shows that the standard error range from 2.34 to 3.67 and that both the Experimental Group and Control Group B performed significantly better in the post-test. The post-hoc LSD test shows the post-test mean scores of the Experimental Group and Control Group A to be significant at a very high level (p<0.000). However, the analysis further indicates that there is no statistically significant difference between the post-test mean scores of the Experimental Group and Control Group B, with a p value of p = 0.32.