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Table 1 The constructs of the original and modified IMB model

From: Modeling predictors of risky drug use behavior among male street laborers in urban Vietnam

Constructs References Number of items Scale Crobach’s α
The original model     
HIV preventive information [21, 22] 7 True/false 0.63
  Transmission information   3 True/false 0.66
  Heuristic information   4 True/false 0.61
HIV preventive motivation [2325] 21 5-point semantic 0.91
  Attitudes   7 5-point semantic 0.75
  Social norms   7 5-point semantic§ 0.83
  Intentions   7 5-point semantic 0.81
HIV preventive behavioral skills [23, 26] 5 5-point semantic# 0.86
  Skill 1 (preparation)   3 5-point semantic# 0.76
  Skill 2 (practice)   2 5-point semantic# 0.91
The modified model     
3 constructs of the original model     
Psychosocial stress‡   4 Different scales 0.71
  Mobility index‡ [27] 2 - -
  Social isolationŸ [28] 6 5-point 0.74
  Alcohol use¥ [29] 2 - 0.60
  Depressionƒ [3034] 10 4-point 0.88
  1. Note: ¶ scale from 1 (negative evaluation) to 5 (positive evaluation); §scale from 1 (negative evaluation) to 5 (positive evaluation); †scale from 1 (very unlikely) to 5 (very likely); #scale from 1 (very hard) to 5 (very easy); ‡ the ratio of the number of migratory cities to years of total migration. (−) Not applicable as it is a ratio; Ÿscale from 0 (not at all) to 4 (almost always) during the past 4 weeks; ¥ a composite of the number of standard drinks and frequency of use over the past 4 weeks; ƒscale from 0 (rarely or none of the time) to 3 (most or all of the time) during the past week.
  2. ‡because the four indicators were associated with stresses given our qualitative findings [20, 35] and statistic parameters (Pearson’s correlation coefficients from the current quantitative data), they were formed to serve as a latent construct of psychosocial stress (α = .71).
  3. All of the above measures have been adapted from the tools by other authors as well as from our qualitative research.