prec_or: Sample size or precision for an odds ratio
In a-lenz/presize: Precision Based Sample Size Calculation

Description Usage Arguments Details Value References

View source: R/differences.R

prec_or returns the sample size or the precision for the provided proportions

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prec_or(p1, p2, n1 = NULL, r = 1, conf.width = NULL,
  conf.level = 0.95, method = c("gart", "woolf", "indip_smooth"),
  tol = .Machine$double.eps^0.25)

`p1`	Risk among unexposed
`p2`	Risk among exposed
`n1`	Number of patients in unexposed group
`r`	allocation ratio (relative size of unexposed and exposed cohort (`n1` / `n2`))
`conf.width`	precision (the full width of the conficende interval)
`conf.level`	confidence level
`method`	Exactly one of `indip_smooth` (default), `gart`, or `wolf`. Methods can be abbreviated.
`tol`	numerical tolerance used in root finding, the default providing (at least) four significant digits

Exactly one of the parameters n, conf.width must be passed as NULL, and that parameter is determined from the other.

Woolf (woolf), Gart (gart), and Independence-smoothed logit (indip_smooth) belong to a general family of adjusted confidence intervals, adding 0 (woolf) to each cell, 0.5 (gart) to each cell, or an adjustment for each cell based on observed data (independence-smoothed). In gart and indip_smooth, estimate of the CI is not possible if p1 = 0, in which case the OR becomes 0, but the lower level of the CI is > 0. Further, if p1 = 1 and p2 < 1, or if p1 > 0 and p2 = 0, the OR becomes ∞, but the upper limit of the CI is finite. For the approximate intervals, gart and indip_smooth are the recommended intervals (Fagerland et al. 2011).

uniroot is used to solve n for the woolf, gart, and indip_smooth method.

Object of class "presize", a list of arguments (including the computed one) augmented with method and note elements.

Fagerland MW, Lydersen S, Laake P (2015). Recommended confidence intervals for two independent binomial proportions. Statistical Methods in Medical Research, 24(2):224-254. doi:10.1177/0962280211415469

a-lenz/presize documentation built on May 17, 2019, 7:44 a.m.