title: The influence of graphic display format on the interpretations of quantitative risk information among adults with lower education and literacy: a randomized experimental study.
abstract: To test optimal graphic risk communication formats for presenting small probabilities using graphics with a denominator of 1000 to adults with lower education and literacy.
  
  
  
  A randomized experimental study, which took place in adult basic education classes in Sydney, Australia. The participants were 120 adults with lower education and literacy. An experimental computer-based manipulation compared 1) pictographs in 2 forms, shaded "blocks" and unshaded "dots"; and 2) bar charts across different orientations (horizontal/vertical) and numerator size (small <100, medium 100-499, large 500-999). Accuracy (size of error) and ease of processing (reaction time) were assessed on a gist task (estimating the larger chance of survival) and a verbatim task (estimating the size of difference). Preferences for different graph types were also assessed.
  
  
  
  Accuracy on the gist task was very high across all conditions (>95%) and not tested further. For the verbatim task, optimal graph type depended on the numerator size. For small numerators, pictographs resulted in fewer errors than bar charts (blocks: odds ratio [OR] = 0.047, 95% confidence interval [CI] = 0.023-0.098; dots: OR = 0.049, 95% CI = 0.024-0.099). For medium and large numerators, bar charts were more accurate (e.g., medium dots: OR = 4.29, 95% CI = 2.9-6.35). Pictographs were generally processed faster for small numerators (e.g., blocks: 14.9 seconds v. bars: 16.2 seconds) and bar charts for medium or large numerators (e.g., large blocks: 41.6 seconds v. 26.7 seconds). Vertical formats were processed slightly faster than horizontal graphs with no difference in accuracy. Most participants preferred bar charts (64%); however, there was no relationship with performance.
  
  
  
  For adults with low education and literacy, pictographs are likely to be the best format to use when displaying small numerators (<100/1000) and bar charts for larger numerators (>100/1000).
authors.affiliation: Screening and Test Evaluation Program, Centre for Medical Psychology and Evidence-based Decision Making (KJM, AD, AH, JJ, SS)
authors.forename: Kirsten J
authors.initials: KJ
authors.lastname: McCaffery
authors.affiliation: Screening and Test Evaluation Program, Centre for Medical Psychology and Evidence-based Decision Making (KJM, AD, AH, JJ, SS)
authors.forename: Ann
authors.initials: A
authors.lastname: Dixon
authors.affiliation: Screening and Test Evaluation Program, Centre for Medical Psychology and Evidence-based Decision Making (KJM, AD, AH, JJ, SS)
authors.forename: Andrew
authors.initials: A
authors.lastname: Hayen
authors.affiliation: Screening and Test Evaluation Program, Centre for Medical Psychology and Evidence-based Decision Making (KJM, AD, AH, JJ, SS)
authors.forename: Jesse
authors.initials: J
authors.lastname: Jansen
authors.affiliation: Screening and Test Evaluation Program, Centre for Medical Psychology and Evidence-based Decision Making (KJM, AD, AH, JJ, SS)
authors.forename: Sian
authors.initials: S
authors.lastname: Smith
authors.affiliation: School of Public Health (JMS), University of Sydney, Sydney, NSW, Australia
authors.forename: Judy M
authors.initials: JM
authors.lastname: Simpson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001296:Audiovisual Aids; D003142:Communication; D003657:Decision Making; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010353:Patient Education as Topic / Q000379:methods*; D018570:Risk Assessment; D055815:Young Adult