# d_weights: Diagnosticity ratio weights In r4lineups: Statistical Inference on Lineup Fairness

## Description

Function to compute weights of each diagnosticity ratio for k lineup pairs

## Usage

 `1` ```d_weights(linedf) ```

## Arguments

 `linedf` A dataframe of parameters for computing diagnosticity ratio

## Details

In order to obtain a pooled estimate of a set of diagnosticity ratios, we use a weight for each ratio that is equal to the inverse of its variance.

To get linedf, use the diag_param helper function

diag_param returns a dataframe containing the following:

• n11: Number of mock witnesses who identified the suspect in the target present condition

• n21: Number of mock witnesses who did not identify the suspect in the target present condition

• n12: Number of mock witnesses who identified the suspect in the target absent condition

• n13: Number of mock witnesses who did not identify the suspect in the target absent condition

## Value

A dataframe with one column containing weights for each pair of lineups for which diagnosticity ratio is being calculated.

## References

Tredoux, C. G. (1998). Statistical inference on measures of lineup fairness. Law and Human Behavior, 22(2), 217-237.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30``` ```#Target present data: A <- round(runif(100,1,6)) B <- round(runif(70,1,5)) C <- round(runif(20,1,4)) lineup_pres_list <- list(A, B, C) rm(A, B, C) #Target absent data: A <- round(runif(100,1,6)) B <- round(runif(70,1,5)) C <- round(runif(20,1,4)) lineup_abs_list <- list(A, B, C) rm(A, B, C) #Pos list lineup1_pos <- c(1, 2, 3, 4, 5, 6) lineup2_pos <- c(1, 2, 3, 4, 5) lineup3_pos <- c(1, 2, 3, 4) pos_list <- list(lineup1_pos, lineup2_pos, lineup3_pos) rm(lineup1_pos, lineup2_pos, lineup3_pos) #Nominal size: k <- c(6, 5, 4) #Use diag param helper function to get data (n11, n21, n12, n22): linedf <- diag_param(lineup_pres_list, lineup_abs_list, pos_list, k) #Call: wi <- d_weights(linedf) ```

r4lineups documentation built on May 2, 2019, 7:10 a.m.