Based on the aforementioned data, the risk index (RI) identifies the percentage of all students of a given racial/ethnic group in a given disability category. The RI is calculated by dividing the number of students in a given racial/ethnic group served in a given disability category (e.g. LD) by the total enrollment for that racial/ethnic group in the school population. The 1998 OCR data revealed risk indices for all racial/ethnic groups that were higher for LD than those found for MR. The NRC (2002) report stated that, “Asian/Pacific Islander have placement rates of 2.23%. Rates for all other racial/ethnic groups exceed 6%, and for American Indian/Alaskan Natives, the rate reached 7.45%” (p. 47). The second index, odds ratio, provides a comparative index of risk and is calculated by dividing the risk index on one racial/ethnic group by the risk index of another racial/ethnic group. In the OCR and OSEP databases, the odds ratios are reported relative to White students. If the risk index is identical for a particular minority group and White students, the odds ratio will equal 1.0. Odds ratios greater than 1.0 indicate that minority group students are at a greater risk of identification, while odds ratios of less than 1.0 indicate that they are less at risk. Using the 1998 OCR placement rates, the LD odds ratio for American Indian/Alaskan Natives is 1.24, showing that they have a 24% greater likelihood of being assigned to the LD category than White students. Odds ratios for Asian/Pacific Islander are low (0.37). For both Black and Hispanic students, the odds ratios are close to 1.0. The third index, composition index (CI), shows the proportion of all children served under a given disability category who are members of a given racial/ethnic group and is calculated by dividing the number of students of a given racial or ethnic group enrolled in a particular disability category. Two underlying assumptions of the CI are that the sum of composition indices for the five racial/ethnic groups will total 100%, and baseline enrollment of a given racial/ethnic group is not controlled. More specifically, the CI may be calculated using the percent of 6- through 21-year old population with the racial/ethnic composition of IDEA and U.S. census population statistics. For example, if 64% of the U.S. population is White, 15% is Black, 16% is Hispanic, 4% is Asian, and 1% is American Indian these data not interpretable without knowing the percentage of the racial/ethnic composition with IDEA. Hypothetically, IDEA data may show that of the 6–21 year olds served under IDEA, 63% are White, 20% are Black, 14% are Hispanic, 2% are Asian, and 1% is American Indian. To calculate disproportionality, a benchmark (e.g. 10%) against which to measure the difference between these percentages must be used. If the difference between the two percentages and the difference represented as a proportion of the group’s percent of population exceeds +10, then the racial/ethnic group is overrepresented. Conversely, if the difference between the two percentages and the difference represented as a proportion of the group’s percent of the population is larger than −10, then, the racial/ethnic group is underrepresented.
Obiakor, F.E. and Utley, C.A. (2005), "MULTICULTURAL LEARNERS WITH LEARNING DISABILITIES: BEYOND EUROCENTRIC PERSPECTIVES", Burkhardt, S., Obiakor, F. and Rotatori, A.F. (Ed.) Current Perspectives on Learning Disabilities (Advances in Special Education, Vol. 16), Emerald Group Publishing Limited, Bingley, pp. 35-64. https://doi.org/10.1016/S0270-4013(04)16003-0Download as .RIS
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