multibias (version 1.6.3)

adjust_sel: Adust for selection bias.

Description

adjust_sel returns the exposure-outcome odds ratio and confidence interval, adjusted for selection bias.

Usage

adjust_sel(
  data_observed,
  data_validation = NULL,
  s_model_coefs = NULL,
  level = 0.95
)

Value

A list where the first item is the odds ratio estimate of the effect of the exposure on the outcome and the second item is the confidence interval as the vector: (lower bound, upper bound).

Arguments

data_observed

Object of class data_observed corresponding to the data to perform bias analysis on.

data_validation

Object of class data_validation corresponding to the validation data used to adjust for bias in the observed data. Here, the validation data should have data for the same variables as in the observed data, plus data for the selection indicator representing whether the observation was selected in data_observed.

s_model_coefs

The regression coefficients corresponding to the model: logit(P(S=1)) = β₀ + β₁X + β₂Y, where S represents binary selection, X is the exposure, and Y is the outcome. The number of parameters is therefore 3.

level

Value from 0-1 representing the full range of the confidence interval. Default is 0.95.

Details

Bias adjustment can be performed by inputting either a validation dataset or the necessary bias parameters. Values for the bias parameters can be applied as fixed values or as single draws from a probability distribution (ex: rnorm(1, mean = 2, sd = 1)). The latter has the advantage of allowing the researcher to capture the uncertainty in the bias parameter estimates. To incorporate this uncertainty in the estimate and confidence interval, this function should be run in loop across bootstrap samples of the dataframe for analysis. The estimate and confidence interval would then be obtained from the median and quantiles of the distribution of odds ratio estimates.

Examples

df_observed <- data_observed(
  data = df_sel,
  exposure = "X",
  outcome = "Y",
  confounders = "C1"
)

# Using validation data -----------------------------------------------------
df_validation <- data_validation(
  data = df_sel_source,
  true_exposure = "X",
  true_outcome = "Y",
  confounders = "C1",
  selection = "S"
)

adjust_sel(
  data_observed = df_observed,
  data_validation = df_validation
)

# Using s_model_coefs -------------------------------------------------------
adjust_sel(
  data_observed = df_observed,
  s_model_coefs = c(0, 0.9, 0.9)
)