Relationship Between Verbal and Performance IQ Among Students with Special Learning Needs

Relationship Between Verbal and Performance IQ Among Students with Special Learning Needs

Cedric B. Stewart

Relationship Between Verbal and Performance IQ Among Students with Special Learning Needs

''Research Questions''

The following research questions were addressed in this study: (a) what is the relationship between Verbal and Performance IQ among students with special learning needs?, and (b) what is the relationship of Verbal IQ of students with special learning needs and each of the five Verbal subtest that make it up? which verbal subtest best represents the Verbal IQ? which Verbal subtests least represents the Verbal IQ?

Results

Continuous interval level data was used to examine both the relationship between Verbal and Performance IQ scores as well as Verbal IQ scores and their corresponding five subtests. Mean and standard deviation scores are located in Table 1. The execution of a scatterplot revealed a generally positive linear relationship between the dependent variables. Standardized skewness coefficients (i.e., skewness divided by the standard error or skewness) for Verbal and Performance IQ were 0.39 and – 2.49 and standardized kurtosis coefficients (i.e., kurtosis divided by the standard error of kurtosis) were 1.00 and 0.51, respectively. These scores fell within the ranges of -3.00 and 3.00 suggesting normality (Onwuegbuzie & Daniel, 2002). However, even though Verbal 1 (Information) and Verbal 4 (Vocabulary) standardized skewness coefficients 4.24 and 4.76, respectively, revealed positively skewed distribution scores outside of these ranges, their levels of kurtosis were within range of normalicy (see Table 1). This assumption of a linear association justified the use of a consecution of Pearson’s product-moment correlation coefficients (i.e. Pearson’s rs).

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Insert Table 1 about here

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Customarily, the alpha level is set at .05 to test for significance. In this case, however, a Bonferroni adjustment was utilized to account for the multiple Pearson rs and computed by taking this normal alpha score and dividing by 6 (i.e., .05/6 = .008). For a result to be statistically significant, the adjusted level must be at or below .008. Using this adjusted alpha level, all six relationships were examined and indicated statistical significance (see Table 2). In particular, a statistically significant relationship between Verbal IQ and Performance IQ was found to exist and is represented by r (1,179) = .66, p < .008. Verbal IQ was also statistically related to its corresponding five subsets which contained varying positive correlation coefficients ranging from .72 for Verbal 3 (Arithmetic) to .85 for Verbal 4 (Vocabulary) and can be found in Table 2.

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Using Cohen’s (1988) criteria, the relationship for the entire data set (i.e., a range of r = .66 to r = .85) suggested a large effect size. Variance of 44.09% for Verbal IQ and Performance IQ was obtained by squaring the correlation coefficients. Therefore, these results suggested that the scores on one of the instruments are a good predictor for performance level on the other for slightly less than half of the population of students with special needs that were examined. Moreover, variance between Verbal IQ and Verbal subtest ranged from the lowest 52.00% for Verbal 3 (Arithmetic) suggesting the least amount of variance to a high of 71.91% for Verbal 4 (Vocabulary), suggesting that vocabulary performance has the highest correlation to Verbal IQ performance as indicated using this instrument.

References

Cohen, J. (1988). ''Statistical power analysis for the behavioral sciences (2nd ed.).'' , : Erlbaum.

Onwuegbuzie, A. J., & Daniel, L. G. (2002). Uses and misuses of the correlation coefficient. Research in the Schools, 9(1), 73-90.

Table 1

''Means, Standard Deviation, Standardized Skewness, and Standardized Kurtosis Coefficients''

Table 2

''Pearson Correlation Matrix of Verbal IQ, Performance IQ, and Verbal Subtests Scores''

Relationships Note. Verbal 1 = Verbal 1 (Information); Verbal 2 = Verbal 2 (Similarities); Verbal 3 = (Arithmetic); Verbal 4 = Verbal 4 (Vocabulary); and Verbal 5 = Verbal 5 (Comprehension).

*Pearson correlation coefficient was statistically significant after the Bonferroni

adjustment was made to account for changes in the alpha level.

Appendix

SPSS Statistical Output