The Optimized Summed Scored Attributes Method for the Classification of U.S. Blacks and Whites: A Validation Study

Area of Science:

• Forensic anthropology
• Biological anthropology
• Human skeletal variation

Background:

• The optimized summed scored attributes (OSSA) method was developed to estimate ancestry in U.S. Black and White populations using cranial morphoscopic traits.
• Dichotomizing trait scores is a key component of the OSSA method for maximizing between-group differences.

Purpose of the Study:

• To test the efficacy of the OSSA method on independent skeletal samples.
• To evaluate the optimal sectioning point for differentiating U.S. Black and White populations using OSSA.

Main Methods:

• The OSSA method was applied to three independent skeletal datasets: Hamann-Todd (n=208), Mercyhurst University (n=28), and the New York City Office of Chief Medical Examiner (n=38).
• Trait frequencies were analyzed to determine the most effective sectioning point for dichotomizing scores.
• Classification accuracy and bias were assessed using both the original (≤3) and a modified (≤4) sectioning points.

Main Results:

• Using the original sectioning point (≤3), the total correct classification rate was 73.0% (Black=50.9%, White=89.2%).
• A modified sectioning point (≤4) increased the total correct classification rate to 79.2% (Black=80.2%, White=78.5%).
• The modified sectioning point also reduced classification bias between the Black and White ancestry groups.

Conclusions:

• The study suggests modifying the sectioning point for the OSSA method from ≤3 to ≤4.
• The modified sectioning point of ≤4 improves overall classification accuracy and reduces bias in forensic ancestry estimation for U.S. Black and White individuals.
• This adjustment is recommended for assessing ancestry in forensic casework.