Compute degrees of freedom according to the Barnard-Rubin formula.
Usage
rubin_df(v_com, var_b, var_t, M)
Arguments
- v_com
Positive number representing the degrees of freedom in the complete-data analysis.
- var_b
Between-imputation sample variance of the point estimates across multiply imputed datasets.
- var_t
Estimate (according to Rubin's rules) of the variance of the point estimates.
- M
Number of imputations (integer larger than 1).
Value
Degrees of freedom according to Barnard-Rubin formula. See Barnard-Rubin (1999).
Details
The computation takes into account limit cases where there is no missing data
(i.e. the between-variance var_b is zero) or where the complete-data degrees of freedom is
set to Inf. Moreover, if v_com is given as NA, the function returns Inf.
References
Barnard, J. and Rubin, D.B. (1999).
Small sample degrees of freedom with multiple imputation. Biometrika, 86, 948-955.
