# Variance of ln of diagnosticity ratio Function to compute variance of ln(d) for k lineup pairs ```r var_lnd(linedf) ``` ## Arguments - `linedf`: A dataframe of parameters for computing diagnosticity ratio ## Returns A dataframe containing ln of the variance of the diagnosticity ratio for each lineup. ## Details 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 ## Examples ```r #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: var <- var_lnd(linedf) ``` ## References Malpass, R. S. (1981). Effective size and defendant bias in eyewitness identification lineups. **Law and Human Behavior, 5**(4), 299-309. Malpass, R. S., Tredoux, C., & McQuiston-Surrett, D. (2007). Lineup construction and lineup fairness. In R. Lindsay, D. F. Ross, J. D. Read, & M. P. Toglia (Eds.), **Handbook of Eyewitness Psychology, Vol. 2: Memory for people** (pp. 155-178). Mahwah, NJ: Lawrence Erlbaum Associates. Tredoux, C. G. (1998). Statistical inference on measures of lineup fairness. **Law and Human Behavior, 22**(2), 217-237. Tredoux, C. (1999). Statistical considerations when determining measures of lineup size and lineup bias. **Applied Cognitive Psychology**, 13, S9-S26. Wells, G. L.,Leippe, M. R., & Ostrom, T. M. (1979). Guidelines for empirically assessing the fairness of a lineup. **Law and Human Behavior, 3**(4), 285-293.

var_lnd function