# asypow: Calculating the asymptotic power and variance In survSNP: Power Calculations for SNP Studies with Censored Outcomes

## Description

This function calculates the asymptotic power and variance assuming that the survival distribution is a mixture of exponentials with rates and the censoring distribution is uniform on the interval (a,b).

## Usage

 `1` ```asypow(n, theta, a, b, lambda0, q, p, alpha, z,exactvar) ```

## Arguments

 `n` Sample size `theta` Effect size (log genotype hazard ratio (GHR)) `a` Censoring distribution parameter (assumed to be uniform on [a,b]) `b` Censoring distribution parameter (assumed to be uniform on [a,b]) `lambda0` Baseline exponential hazard rate `q` Relative risk allele frequency `p` Relative genotype frequency `alpha` Nominal two-sided type I error rate `z` Genotype scores (right now only additive scores AA=0,AB=1,BB=2 generate correct power) `exactvar` Indicator for using the exact variance formula

## Details

This function is called by sim.snp.expsurv.power to calculate the asymptotic variance (exact and approximate) formulas. It is not intended to be called directly by the user. To conduct power calculations, use sim.snp.expsurv.power or the convenience wrapper function survSNP.power.table.

## Value

 `power` Asymptotic power based on exact variance formula `power0` Asymptotic power based on approximate variance formula `v1` First term of asymptotic variance `v2` Second term of asymptotic variance `v12` Third term of the asymptotic variance (covariance) `vapprox` Approximate asymptotic variance formula (=v1) `exact` Exact asymptotic variance formula (=v1+v2+v12) `diff` Difference between variances (=v2+v12) `ratio` Ratio of variances (=v1/(v1+v2+v12))

## Author(s)

Kouros Owzar, Zhiguo Li, Nancy Cox, Sin-Ho Jung and Chanhee Yi

## References

Kouros Owzar, Zhiguo Li, Nancy Cox and Sin-Ho Jung. Power and Sample Size Calculations for SNP Association Studies with Censored Time-to-Event Outcomes. http://onlinelibrary.wiley.com/doi/10.1002/gepi.21645/abstract

survSNP documentation built on May 2, 2019, 2:48 p.m.