title: New non-randomised model to assess the prevalence of discriminating behaviour: a pilot study on mephedrone.
abstract: BACKGROUND
  An advantage of randomised response and non-randomised models investigating sensitive issues arises from the characteristic that individual answers about discriminating behaviour cannot be linked to the individuals. This study proposed a new fuzzy response model coined 'Single Sample Count' (SSC) to estimate prevalence of discriminating or embarrassing behaviour in epidemiologic studies.
  
  
  METHODS
  The SSC was tested and compared to the established Forced Response (FR) model estimating Mephedrone use. Estimations from both SSC and FR were then corroborated with qualitative hair screening data. Volunteers (n = 318, mean age = 22.69 ± 5.87, 59.1% male) in a rural area in north Wales and a metropolitan area in England completed a questionnaire containing the SSC and FR in alternating order, and four questions canvassing opinions and beliefs regarding Mephedrone. Hair samples were screened for Mephedrone using a qualitative Liquid Chromatography-Mass Spectrometry method.
  
  
  RESULTS
  The SSC algorithm improves upon the existing item count techniques by utilizing known population distributions and embeds the sensitive question among four unrelated innocuous questions with binomial distribution. Respondents are only asked to indicate how many without revealing which ones are true. The two probability models yielded similar estimates with the FR being between 2.6% - 15.0%; whereas the new SSC ranged between 0% - 10%. The six positive hair samples indicated that the prevalence rate in the sample was at least 4%. The close proximity of these estimates provides evidence to support the validity of the new SSC model. Using simulations, the recommended sample sizes as the function of the statistical power and expected prevalence rate were calculated.
  
  
  CONCLUSIONS
  The main advantages of the SSC over other indirect methods are: simple administration, completion and calculation, maximum use of the data and good face validity for all respondents. Owing to the key feature that respondents are not required to answer the sensitive question directly, coupled with the absence of forced response or obvious self-protective response strategy, the SSC has the potential to cut across self-protective barriers more effectively than other estimation models. This elegantly simple, quick and effective method can be successfully employed in public health research investigating compromising behaviours.
authors.affiliation: School of Life Sciences, Kingston University, UK. A.Petroczi@kingston.ac.uk
authors.forename: Andrea
authors.initials: A
authors.lastname: Petróczi
authors.forename: Tamás
authors.initials: T
authors.lastname: Nepusz
authors.forename: Paul
authors.initials: P
authors.lastname: Cross
authors.forename: Helen
authors.initials: H
authors.lastname: Taft
authors.forename: Syeda
authors.initials: S
authors.lastname: Shah
authors.forename: Nawed
authors.initials: N
authors.lastname: Deshmukh
authors.forename: Jay
authors.initials: J
authors.lastname: Schaffer
authors.forename: Maryann
authors.initials: M
authors.lastname: Shane
authors.forename: Christiana
authors.initials: C
authors.lastname: Adesanwo
authors.forename: James
authors.initials: J
authors.lastname: Barker
authors.forename: Declan P
authors.initials: DP
authors.lastname: Naughton
mesh_terms: D000328:Adult; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000032:analysis; D003430:Cross-Sectional Studies / Q000706:statistics & numerical data; D005260:Female; D006197:Hair / Q000737:chemistry; D006306:Health Surveys / Q000379:methods / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000032:analysis; D015233:Models, Statistical; D010865:Pilot Projects; D015203:Reproducibility of Results; D012651:Self Medication / Q000523:psychology / Q000706:statistics & numerical data*
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine; C548233:mephedrone