presize (version 0.3.9)

prec_lim_agree: Sample size or precision for limit of agreement on Bland-Altman plots

Description

prec_lim_agree returns the sample size or the precision for the limit of agreement, i.e. the confidence interval around the limit of agreement, expressed in SD-units. It is an approximation based on the Normal distribution, instead of a Student t distribution.

Usage

prec_lim_agree(n = NULL, conf.width = NULL, conf.level = 0.95)

Value

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

Arguments

n

sample size.

conf.width

precision (the full width of the confidence interval).

conf.level

confidence level.

Details

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

The sample size and precision are calculated according to formulae in Bland & Altman (1986). The CI width is a simple function of the sample size only.

References

Bland & Altman (1986) Statistical methods for assessing agreement between two methods of clinical measurement Lancet i(8476):307-310 tools:::Rd_expr_doi("10.1016/S0140-6736(86)90837-8")

Examples

# calculate confidence interval width, given N
prec_lim_agree(200)
# calculate N given, confidence interval width
prec_lim_agree(conf.width = .1)