Symbols were superior to numbers for presenting strength of recommendations to health care consumers: a randomized trial

OBJECTIVE: To compare health care consumers' understanding, evaluations, and preferences for symbols vs. numbers and letters for the representation of strength of recommendations (SOR) and quality of evidence (QOE). STUDY DESIGN AND SETTING: Questionnaire study in a randomized controlled design in the setting of a community health education program. RESULTS: Eighty-four participants completed the questionnaire. For the presentation of the SOR, participants had better objective understanding of symbols than numbers (74% vs. 14%, P<0.001). They also scored symbols positively, and numbers negatively for ease of understanding (mean difference [md]=1.5, P=0.001), clearness and conciseness (md=1.5, P<0.001), and conveyance of the degree of uncertainty (md=0.7, P=0.092). About half (48%) preferred symbols over numbers. For the presentation of the QOE, objective understanding of symbols and letters was similar (91% vs. 95%, P=0.509). Participants scored both symbols and letters positively; the scores for symbols were however lower for ease of understanding (md=-0.7, P=0.019), clearness and conciseness (md=-0.6, P=0.051), and conveyance of the QOE (md=-0.4, P=0.24). CONCLUSION: Symbols were superior to numbers for the presentation of the SOR. Objective understanding was high for both symbols and letters for the presentation of the QOE, but letters conveyed the QOE better than symbols.