Confidence intervals for lineup proportion

Computes bootstrapped confidence intervals for lineup proportion

Usage

lineup_boot_allprop(lineup_vec, k, conf = 0.95, R = 1000)

Arguments

lineup_vec

A numeric vector of lineup choices

k

Number of targets in lineup. Must be specified by user (scalar).

conf

Confidence level for the intervals, e.g. 0.95 for 95 percent intervals. Defaults to 0.95. May be specified by user (scalar).

R

Number of bootstrap replications. Defaults to 1000.

Value

A dataframe of k rows and two columns, ci_low and ci_high, holding the bias-corrected and accelerated (BCa) confidence interval for the proportion choosing each lineup member. Rows are named by lineup position.

Details

Computes a bootstrapped lineup proportion for each member in turn by calling the boot function in the boot package. Where a BCa interval cannot be computed, the percentile interval is used instead.

Note that the k intervals are each computed at the nominal conf level, with no adjustment for the fact that k of them are inspected together. Interpreting all of them at once inflates the chance that at least one excludes the chance value by more than the nominal amount. If a family-wise statement is wanted, raise the level for each interval accordingly, e.g. conf = 1 - 0.05 / k for a Bonferroni-style correction.

References

Davison, A.C. & Hinkley, D.V. (1997). Bootstrap methods and their application. Cambridge University Press.

Wells, G. L., Leippe, M. R., & Ostrom, T. M. (1979). Guidelines for assessing the fairness of a lineup. Law and Human Behavior, 3(4), 285-293.

See also

boot: https://cran.r-project.org/web/packages/boot/boot.pdf

Examples

#Data:
lineup_vec <- round(runif(100, 1, 6))

#Call:
lineuprops_ci <- lineup_boot_allprop(lineup_vec, k= 6)
lineuprops_ci <- lineup_boot_allprop(lineup_vec, k= 6, conf = 0.975)