DOBLE CARGA DE PROBLEMAS NUTRICIONALES

The purpose of this study was to explore the effect of a vocabulary instructional intervention on vocabulary acquisition. This study employed a quasi-experimental design involving 73 fifth-grade English learners who were situated in 11 classrooms. The

classrooms were randomly assigned to an intervention treatment group (n = 6) or a

comparison group (n = 5). The question that this research sought to answer was: Is there a difference in vocabulary acquisition between English learners in a treatment group

incorporating purposeful and strategic communicative instructional techniques with explicit teacher explanations of new vocabulary terms and communicative tasks as recommended in the research into vocabulary instruction from a core reading program and those in a standard vocabulary -instruction comparison group? Communicative student tasks of the treatment included student-generated descriptions of new vocabulary terms, nonlinguistic representations, word associations, teacher-directed word analysis and graphic organizers. The peer-mediated activities were accomplished by two methods, the joint completion of the graphic organizer and the review games. The graphic

organizer was the basis for the peer-mediated structure and required a description, a nonlinguistic representation of the word, an example, nonexample, and word analysis. This study used a pretest-posttest design with the vocabulary mastery pretest at the beginning of the study in September and a mastery posttest at the end of the study in December. This study also measured weekly vocabulary development through weekly vocabulary assessments used in the core reading program.

Descriptive Statistics Results for Measures

Descriptive statistics including distributions, correlations, measures of central tendency, and dispersion were calculated for vocabulary mastery measures and weekly quizzes.

Overall Vocabulary Growth

The mastery test was used to measure overall vocabulary acquisition of words from the core reading program. It was administered at the beginning of the study in September and again at the conclusion of the study in December. The mastery test consisted of 28 multiple choice questions drawn from the vocabulary assessments in the core reading program. The questions were randomly selected from the first 15 reading selections of the core reading program. The response consisted of students choosing from four options that correctly identified the meaning of the vocabulary word underlined in the sentence (see Appendix F).

Assumptions of Normality

Examination of the score distributions revealed that scores were approximately normally distributed on the mastery pretest and posttest. Tests of normality showed that the prescores and postscores did not differ significantly from 0, indicating a normal distribution (see Table 4.1). Scores ranged from 3 to 19 at pretest and ranged from 6 to 26 at posttest. Examination of outliers for the pretest showed two students in the comparison group scored two standard deviations above the mean, with scores of 18 and19, and one

Table 4.1

Test of Normality for Mastery Test

Test Skewness SE Kurtosis SE

Pretest .157 .281 .369 .555 Posttest -.184 .281 -.116 .555

student in the treatment group scored two standard deviations below the mean with a score of three. For the posttest, one student scored two standard deviations above the mean with a score of 26. Although the student scored two standard deviations above the mean, a histogram showed that this score was not an extensively atypical outlier as there were 10 scores that were just one to four points below the score of 26 (see Figure 4.1). All of these students’ scores were from the treatment group. Two scores were two standard deviations below the mean with a score of 6.

Correlations

A correlation analysis measures the linear relationship between two variables. If there is a relationship, as one variable increases or decreases the second variable

increases or decreases by a consistent and predictable amount. Correlations were analyzed on the mastery test between pretest (time 1) and posttest (time 2) to determine the relationship between time 1 and time 2 for the mastery test. A scatterplot showed that there was a positive linear relationship between the pretest scores and the posttest scores, albeit not a strong one (Figure 4.2). Table 4.2 displays the results of the analysis that revealed a significant relationship between time 1 and time 2, r = +.385, n = 73, p < .01, two-tailed. Calculating r2 _{showed that only 12% of the variability of the posttest scores} could be explained by the pretest scores.

Figure 4.2. Scatterplot of mastery test scores.

Table 4.2

Correlations of Mastery Tests

Time 2 1 .385

Descriptive Statistics

On the mastery test, there was a possible range of scores from 0 to 28. The means were calculated for the pretest (M = 10.96, SD = 2.91) and the posttest (M = 16.70, SD = 4.35). Average gain between the pretest and the posttest was 5.68 points (Table 4.3).

Descriptive Statistics by Group

There was not a significant difference between the means of the treatment (M = 10.77. SD = 2.56) and comparison group (M = 11.31, SD = 3.47) on the mastery pretest. The comparison group scored higher than the treatment group on the pretest with a difference of .54 points.

Table 4.3

Descriptive Statistics for Mastery Test

Variable N Mean SE Median SD Variance Minimum Maximum

Pretest 73 10.96 .34 11 2.91 8.46 3 19

Posttest 73 16.70 .51 17 4.35 18.94 6 26

Gain 5.68 .49 6 4.15 -2 15

On the mastery posttest the treatment group (M = 18.28, SD = 4.02) scored higher than the comparison group (M = 13.85, SD = 3.414). This is a difference of 4.43 points between the means. Students in the treatment group showed higher average scores on the overall mastery gain (M = 7.43, SD = 3.62) than the comparison group (M = 2.54, SD = 3.09). The difference between the two means was 4.89 points. An independent t test showed the difference between the two groups at posttest was significant, t(71) = 5.813, p < .001. Tables 4.4 and 4.5 display descriptive statistics for the mastery test by group. Table 4.6 shows descriptive statistics for treatment and comparison group by time.

Linear Regression

Linear regression was conducted using MPlus Version 5 (Muthén & Muthén, 2007) to examine the potential differences in vocabulary acquisition by group assignment for the overall mastery test. Analysis included a cluster variable to account for teacher grouping. The linear model for the mastery test regressed student posttest scores on pretest scores by group assignment. A chi-square test of model fit for the baseline model was significant, χ2(2, N = 73) = 40.643, p < 0.001, indicating the model was appropriate to significantly predict differences between groups. The model indicated that the group

Table 4.4

Descriptive Statistics for Mastery Pretest by Group

Variable n Mean SE SD Median Minimum Maximum

Pretest 73 10.96 .340 2.908 11 3 19

Treatment 47 10.77 .374 2.564 11 3 15

Comparison 26 11.31 .681 3.473 10.5 6 19

Table 4.5

Descriptive Statistics for Mastery Posttest by Group

Variable n Mean SE SD Median Minimum Maximum

Posttest 73 16.70 .509 4.352 17 6 26

Treatment 47 18.28 .586 4.020 18 9 26

Comparison 26 13.85 .670 3.414 14 6 19

Table 4.6

Descriptive Statistics for Mastery Test by Time

Treatment

───────────────── ───────────────── Comparison Variable Mastery pretest Mastery posttest Mastery pretest Mastery posttest

n 47 47 26 26 Time 1 2 1 2 Mean 10.77 18.28 11.31 13.85 SE .37 .59 .68 .67 SD 2.56 4.02 3.47 3.41 Range—Min 3 9 6 6 Range—Max 15 26 19 19

assignment variable was significant, t(71) = 9.406, p < 0.001. The 95% confidence interval was between 0.385 and 0.675, with a coefficient of 0.530. This analysis revealed a significant difference in growth of vocabulary skills from pretest to posttest between treatment and comparison groups (p = .001). Students in the treatment group showed greater progress than student in the comparison group. When interpreting effect size for

r2 (or the percentage of variance explained), 0.01 is considered a small effect, 0.09 is a

medium effect, and 0.25 is a large effect size (Cohen, 2008; Gravetter & Wallnau, 2008). In this study, group assignment accounted for 36% of the variance in comparing

treatment group to comparison group. These results lend support to the influence of the purposeful and strategic components of the treatment used in this study to help fifth- grade English learners acquire vocabulary knowledge.

Weekly Vocabulary Growth

The weekly quizzes were administered at the beginning and end of each weekly selection cycle. The purpose of the weekly quizzes was to determine if the intervention helped students acquire vocabulary from the core reading program during the weekly vocabulary instruction. Each selection from the core reading program had a weekly vocabulary quiz, with the number of words tested ranging from five to seven. The possible ranges of correct answers were 0 to 5, 6, or 7, depending on the number of vocabulary words tested for that week. The quizzes were multiple choice questions in which the students chose the correct meaning from four options for a word underlined in a sentence.

Assumptions of Normality

Analysis of weekly vocabulary growth focused on weekly gain scores for each of the nine selections taught in all treatment and comparison classes. Gain scores were determined by calculating the average difference in words correct between each weekly pretest and posttest quiz. Gain scores were analyzed for normality (see Figure 4.3). Results of the analysis showed that the gain scores were normally distributed, with scores not differing significantly from zero (see Table 4.7). One student’s average growth score was more than two standard deviations above the mean with 4 points growth on the weekly quiz. No scores fell outside of two standard deviations below the mean (see Figure 4.3).