RRmpWald: Wald confidence intervals for RR from matched pairs

In ABS-dev/PF: Prevented fraction

Wald confidence intervals for RR from matched pairs

Description

Estimates confidence intervals for the risk ratio or prevented fraction from matched pairs.

Usage

RRmpWald(
  formula = NULL,
  data = NULL,
  compare = c("vac", "con"),
  affected = 1,
  x,
  alpha = 0.05,
  pf = TRUE,
  tdist = TRUE,
  df = NULL,
  rnd = 3
)

Arguments

formula	Formula of the form y ~ x + cluster(w), where y is the indicator for an individual's positive response, x is a factor with two levels of treatment, and w identifies the pairs.
data	data.frame containing variables in formula
compare	Text vector stating the factor levels: compare[1] is the vaccinate group to which compare[2] (control or reference) is compared.
affected	Indicator for positive response
x	Alternative data input. Instead of formula and data frame, data may be input as frequency vector. See example for how to order this vector.
alpha	Complement of the confidence level
pf	Estimate RR or its complement PF?
tdist	Use t distribution?
df	Degrees of freedom. When NULL, the function will default to df = N - 2, where N is the total number of pairs.
rnd	Number of digits for rounding. Affects display only, not estimates.

Details

Estimates confidence intervals for the risk ratio or prevented fraction from matched pairs. The response is the tetranomial vector c(11, 12, 21, 22), where the first index is the row and the the second index is the column when displayed as a 2x2 table. Wald type confidence intervals are found by applying the delta method to the multinomial variance. This method fails when there are no responders in one of the treatment groups.

Alternative forms of data entry are illustrated by the output, say
Y, where c(Y$xtable) = Y$freqvec = Y$multvec$Freq.

If RR = 0 (PF = 1), the function will return degenerate interval.

Value

A rrmp object with the following fields:

estimate	vector of point and interval estimates - see details
estimator	either "PF" or "RR"
compare	text vector, same as input
alpha	complement of confidence level
rnd	how many digits to round the display
multvec	data frame showing the multinomial representation of the data

Note

Experimental functions for estimating profile likelihood intervals are in the CVBmisc package.

Call to this function may be one of two formats: (1) specify data and formula or (2) as a vector x

RRmpWald(formula, data, compare = c('vac', 'con'), affected = 1, alpha = 0.05,
pf = TRUE, tdist = TRUE, df = NULL, rnd = 3)

RRmpWald(x, compare = c('vac', 'con'), affected = 1, alpha = 0, 05,
pf = TRUE, tdist = TRUE, df = NULL, rnd = 3)

Author(s)

PF-package

Examples

RRmpWald(pos ~ tx + cluster(cage), New, compare = c('vac', 'con'))

# PF
# 95% interval estimates
#
#    PF    LL    UL
# 0.550 0.183 0.752

require(magrittr)
thistable <- New |>
  tidyr::spread(tx, pos) |>
  dplyr::mutate(vac = factor(vac, levels = 1:0),
    con = factor(con, levels = 1:0)) |>
  with(table(vac, con))
thistable
#    con
# vac  1  0
#   1  7  2
#   0 13  4
as.vector(thistable)
# [1]  7 13  2  4

RRmpWald(x = as.vector(thistable))

# PF
# 95% interval estimates
#
#    PF    LL    UL
# 0.550 0.183 0.752

ABS-dev/PF documentation built on April 26, 2024, 3:29 p.m.