BlindingIndex.jl

Compute James' and Bang's Blinding Indices.

The code is based on R package BI by Marc Schwartz and Nate Mercaldo.

Usage

using BlindingIndex
x = [48 22; 4 30; 330 319]
bi(x)

Output:

BI James     Estimate     Std. Error   LCL      UCL      95% CI, 2-sided
Overall      0.896        0.011        0.875    0.918   

BI Bang      Estimate     Std. Error   LCL      UCL      95% CI, 2-sided
Treatment    0.115        0.018        0.08     0.15    
Placebo      0.022        0.019        -0.016   0.06    

Arguments

• x::Matrix{Int64}: 2×2 or 3×2 integer matrix of cross-tabulated counts
• weights::Matrix{Float64}=[0 0.5; 0.5 0; 1 1]: use default 1996 James weights for 3×2 unless alternative weights are specified; correct guesses are assigned a weight of 0, incorrect guesses are assigned a weight of 0.5, don't know guesses are assigned a weight of 1
• conf::Float64=0.95: confidence level for the returned confidence intervals
• alternative::Symbol=:two: whether two-sided (:two) (the default) or one-sided (:less or :greater) confidence intervals are returned
• groups::Vector{String}=["Treatment", "Placebo"]: treatment group names
• output::Bool=true: if true, show the output

Returns

Named tuple containing:

• bi_james: James' index (overall estimated value, standard error, lower confidence interval bound, upper confidence interval bound)
• bi_bang: Bang's index (estimated values, standard errors, lower confidence interval bounds, upper confidence interval bounds for group 1 and 2)

Notes

The format of the cross-tabulated counts and weights is:

             Treatment  Placebo
Treatment    xxx        xxx 
Placebo      xxx        xxx 
Don't Know   xxx        xxx

If 2×2 cross-tabulated counts matrix is provided, the last row is filled with zeros.

Sources

1. James KE, Bloch DA, Lee KK, Kraemer HC, Fuller RK. An index for assessing blindness in a multi-centre clinical trial: disulfiram for alcohol cessation--a VA cooperative study. Stat Med. 1996 Jul 15;15(13):1421-34. doi: 10.1002/(SICI)1097-0258(19960715)15:13<1421::AID-SIM266>3.0.CO;2-H. PMID: 8841652.
2. Bang H, Ni L, Davis CE. Assessment of blinding in clinical trials. Control Clin Trials. 2004 Apr;25(2):143-56. doi: 10.1016/j.cct.2003.10.016. PMID: 15020033.