Sensitivity of Crosswise Model to Simplistic Selection of Nonsensitive Questions: An Application to Estimate Substance Use, Alcohol Consumption and Extramarital Sex Among Iranian College Students.

BACKGROUND

Nonrandomized response (NRR) models are a new generation of surveys for sensitive issues. This study aims to evaluate the validity of estimates from the crosswise model (as one of the efficient models) through employing different response probabilities of nonsensitive questions.

METHODS

This cross-sectional study was conducted during October and November 2015 among 1777 students of Tabriz University of Medical Sciences. Estimates of monthly alcohol consumption, and at least one instance of illicit drug use and extramarital sex over the last year were determined using direct questioning (DQ) and the Crosswise model (CM). In the last model, the probability of positive response to the nonsensitive questions was determined by using five different methods: uniform distribution (I), Benford's law (II), and estimations based on data from three other studies (III, IV, V).

RESULTS

Crosswise estimates of sensitive behaviors with different probabilities of a positive response to nonsensitive questions differed significantly. For example, estimates of history of using illegal opioids at least once in the last year among men varied significantly from 5.0% to 16.1% with different crosswise models based on the probability of being born in Spring using method I (0.250), III (0.287), IV (0.248), and V (0.310). The model based on Benford's law (II) was applied to estimate alcohol and cannabis consumption, and its estimates showed significant discrepancy with results of crosswise models I and V.

CONCLUSION

Estimates from crosswise model is highly sensitive to the response probability of nonsensitive questions. It seems that if this question is not selected carefully, the mentioned models will provide overestimates or underestimates, and the more-is-better hypothesis is not always valid. To achieve valid estimates, the exact probability of a positive response to the nonsensitive question must be known for the studied population.