Description Usage Arguments Details Value Warning Note Author(s) See Also Examples

The nsibs() function will compute the number of affected sibpairs needed to detect linkage to a susceptibility gene attributed with a user-specified lambda sib (ls) and lambda off (lo). Lambda sib is the recurrence risk ratio for full- sibs (includes dominance variance), lambda off is the recurrence risk ratio for parent- offspring pairs (so does not include dominance variance). In these calculations we assume that parents and sibs are completely genotyped with markers that perfectly define the IBD configurations. alpha and beta correspond to the type 1 and 1 - type 2 error rates respectively.

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`ls` |
the recurrence risk ratio for full-sibs (includes dominance variance). |

`lo` |
the recurrence risk ratio for parent- offspring pairs (so does not include dominance variance) |

`alpha` |
the Type 1 error rate. |

`beta` |
one minus the Type 2 error rate, so (1-beta)=Power. |

In these calculations we assume that parents and sibs are completely genotyped with markers that perfectly define the IBD configurations.

`n ` |
The number of sib pairs needed to obtain the desired power under the chosen study design. |

Makes the simplifying assumptions that (1) all families will have exactly two affected sibpairs; and that (2) the identity-by-descent status in the ASPs can be determined unambiguously

These are based on a Mathematica notebook created by Martin Farrall.

Daniel E. Weeks

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