- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- 04: DNA Amplification
- 05: Amplified DNA Product Separation
- 06: STR Data Analysis & Interpretation
- 07: Population Genetics & Statistics
- 08: Communicating Results
- 09: Other DNA Markers & Technologies
- Course Resources
- Laboratory Training Manual
President's DNA Initiative
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Advancing Justice Through DNA Technology
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Advancing Justice Through DNA Technology
DNA Analyst Training
Theta Correction
Home > Population Genetics & Statistics > Statistics > Theta Correction
In the previous module, inbreeding and population substructure were introduced. Population substructure can be dealt with in the same manner as inbreeding. The NRC II proposed using formulas 4.4a and 4.4b to deal with population substructure. Formulas analogous to those noted below (with theta) are used for the inbreeding coefficient, F. These formulas do not require that the subpopulations be distinct or mate at random.07 The value of theta (θ) can be positive or negative, but must be less than or equal to 1.
Click here to read about the inbreeding coefficient, F in Subject 07, Module 01.
- Homozygote: pi2 + pi (1-pi) θii (formula 4.4a from the NRCII)
- Heterozygote: 2p i pj(1- θij ), i ≠ j (formula 4.4b from the NRCII)
Click here to read about formula 4.4a and 4.4b from NRC II.
The parameter θ can be defined as the probability that two alleles in different people, in the same subpopulation, are identical by descent.05 Strictly the two alleles can originate from the same individual or, more likely, two different individuals. The value of θ can be determined for a given population. Generally, θ = 0.01 can be used for large populations, and θ = 0.03 for small, isolated populations.
