Table 5

Comparison of exact and IBS methods in a particular case

Genotype data

Exact calculation

IBS method

Ratio LR1/LR2

Marker

Sib1

Sib2

Genotype combination⁽¹⁾

Allele frequencies⁽²⁾

Likelihood ratio⁽³⁾

Shared alleles

H⁽⁴⁾

Likelihood ratio⁽⁵⁾

CSF1PO

9–13

9–13

4

p₉ = 0.044

p₁₃ = 0.062

50.93

2

3.52

14.5

FGA

20–24.2

20–24.2

4

p₂₀ = 0.156

p_24.2 = 0.009

103.97

2

9.78

10.6

FES

12–13

12–13

4

p₁₂ = 0.266

p₁₃ = 0.047

13.38

2

2.94

4.6

F13A1

5–5

5–5

1

p₅ = 0.184

10.32

2

3.83

2.7

D19S253

8–12

12–12

2

p₁₂ = 0.369

0.93

1

0.760

0.35

2.7

F13B

6–8

6–10

6

p₆ = 0.080

1.81

1

0.86

2.1

LPL

10–12

10–10

2

p₁₀ = 0.275

1.16

1

0.723

0.89

1.3

TH01

9.3–9.3

9–9.3

2

p_9.3 = 0.241

1.29

1

1.02

1.3

D18S51

13–19

14–17

7

0.25

0

0.25

1.0

D8S1179

13–15

13–15

4

p₁₃ = 0.344

p₁₅ = 0.116

4.82

2

6.07

0.8

TPOX

8–11

8–10

6

p₈ = 0.512

0.49

1

0.78

0.6

VWA

17–18

17–18

4

p₁₇ = 0.275

p₁₈ = 0.206

3.52

2

5.71

0.6

D21S11

63–67

63–65

6

p₆₃ = 0.244

0.76

1

1.17

0.6

Cumulative log(LR)

6.47

2.92

Probability

>99.999%

99.9%

Calculations applied to the most discordant pair from Fig. 2 are fully displayed. ⁽¹⁾from Table 1A; ⁽²⁾calculated from full-sib sample data; ⁽³⁾FS rather than NR, computed using formulas from Table 1A; ⁽⁴⁾computed from sample data; ⁽⁵⁾FS rather than NR, computed from values in Table 3 or applying formulas from Table 2 to the displayed H values.

Presciuttini et al. BMC Genetics 2002 3:23   doi:10.1186/1471-2156-3-23