Self-reported numeracy was a strong predictor of accuracy of responses ( odds ratio [ OR ] = 2.6 , P = 0.008 ) , and the impact of high numeracy varied across graphical type , having a greater impact on line ( OR = 5.1 ; 95 % confidence interval [ CI ] = 1.6-16 ; P = 0.04 ) and pie charts ( OR = 7.1 ; 95 % CI = 2.6-19 ; P = 0.01 ) , without an impact on pictographs ( OR = 0.4 ; 95 % CI = 0.1-1 .7 ; P = 0.17 ) or bar charts ( OR = 0.5 ; 95 % CI = 0.1-1 .8 ; P = 0.24 ) .