|
Size: 712
Comment:
|
Size: 1555
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 1: | Line 1: |
| Line 4: | Line 3: |
| Total sample size may be evaluated for comparing hazard rates (per unit time) using this [attachment:coxsamp.xls spreadsheet] which uses a simple formula taken from Collett (2003) [http://stats.stackexchange.com/questions/7508/power-analysis-for-survival-analysis illustrated here] corresponding to a group regression estimate in a Cox regression model. Alternatively the effect size can be expressed in terms of ratios of group survival rates as used by the power calculator given [http://www.stattools.net/SSizSurvival_Pgm.php here.] | Total sample size may be evaluated for comparing hazard rates (per unit time) using this [attachment:coxsamp.xls spreadsheet] which uses a simple formula taken from Collett (2003) [http://stats.stackexchange.com/questions/7508/power-analysis-for-survival-analysis illustrated here] corresponding to a group regression estimate (ratio of hazards) in a Cox regression model. Alternatively the effect size can be expressed in terms of ratios of group survival rates as used by the power calculator given [http://www.stattools.net/SSizSurvival_Pgm.php here.] |
| Line 6: | Line 5: |
| __Reference__ | In particular Collett(2003) gives the total sample size, d, required as d = $$\frac{(z_text{a/2} + z_text{b/2})^text{2}}{p(1-p)log(hr)^text{2}}$$ for two-sided type I error, ''a'', power ''1-b'', event rate in population ''p'', hazard ratio, ''hr'' and ''z'' the Standard Normal (or probit) function. Hsieh and Lavori (2000) give sample size formulae for the number of deaths using continuous covariates in the Cox regression. d = $$\frac{(z_text{1-a} + z_text{1-b))^text{2}}{\sigma^text{2}\hr^text{2}} dc = dc$$/1-R^text{2}$$ where $$R^text{2}$$ is the squared multiple correlation regression one covaraite on the others. __References__ |
| Line 9: | Line 20: |
Hsieh FY and Lavori PW (2000) Sample size calculations for the Cox proportional hazards regression models with nonbinary covariates ''Controlled Clinical Trials'' '''21''' 552-560. |
Survival analysis sample size calculations
Total sample size may be evaluated for comparing hazard rates (per unit time) using this [attachment:coxsamp.xls spreadsheet] which uses a simple formula taken from Collett (2003) [http://stats.stackexchange.com/questions/7508/power-analysis-for-survival-analysis illustrated here] corresponding to a group regression estimate (ratio of hazards) in a Cox regression model. Alternatively the effect size can be expressed in terms of ratios of group survival rates as used by the power calculator given [http://www.stattools.net/SSizSurvival_Pgm.php here.]
In particular Collett(2003) gives the total sample size, d, required as
d = $$\frac{(z_text{a/2} + z_text{b/2})text{2}}{p(1-p)log(hr)text{2}}$$
for two-sided type I error, a, power 1-b, event rate in population p, hazard ratio, hr and z the Standard Normal (or probit) function.
Hsieh and Lavori (2000) give sample size formulae for the number of deaths using continuous covariates in the Cox regression.
d = $$\frac{(z_text{1-a} + z_text{1-b))text{2}}{\sigmatext{2}\hr^text{2}}
dc = dc$$/1-Rtext{2}$$ where $$Rtext{2}$$ is the squared multiple correlation regression one covaraite on the others.
References
Collett, D (2003) Modelling Survival Data in Medical Research Second Edition. Chapman and Hall:London
Hsieh FY and Lavori PW (2000) Sample size calculations for the Cox proportional hazards regression models with nonbinary covariates Controlled Clinical Trials 21 552-560.