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Table 1 Smokefree signage and dog control signage at 63 children’s playgrounds in 21 contiguous local government authority areas in the lower North Island of New Zealand (for signs within 10 m of the playground equipment)

From: Smokefree signage at children’s playgrounds: Field observations and comparison with Google Street View

Characteristic Smokefree signs [95% CI] Dog control signs [95% CI] P-value for difference
Playgrounds with any sign (N) 28 20
% of all playgrounds with any sign 44% (28/63) 32% (20/63) 0.149
Local government areas with any signs (n = 21 areas) 71% 48% 0.133
Playgrounds in city areas (n = 39) with signs 49% 36% 0.264
Playgrounds in other local government areas (n = 24) 38% 25% 0.373
Total signs (ie, multiple signs in some playgrounds) 50 28
Mean number of signs per playground (SD) 0.79 (1.23) 0.44 (0.80) 0.095
Range for signs per playground (N) 0 to 6 0 to 4
Sign size
 Average in cm2 (SD) 1057 (960) 1154 (1161) 0.749
 Median in cm2 600 768
 Inter-quartile range (cm2) 233 to 1800 440 to 1350
 Full range (cm2) 42 to 2880 100 to 3600
Performance of GSV (using field observations as the gold standard)
 Play equipment not visible on GSV (too far from a road) – these results excluded from further analysis 11 (17.5%) 11 (17.5%)
 True positives [A] 4 7
 True negatives [B] 26 32
 False positives [C]a 1 3
 False negatives [D] 21 10
 Sensitivity [A/(A + D)] 16% [5% – 34%] 41% [20% – 65%] 0.087
 Specificity [B/(B + C)] 96% [83% – 100%] 91% [78% – 98%] 0.505
 Positive predictive value [A/(A + C)] 80% [33% – 99%] 70% [38% – 92%] 0.747
 Negative predictive value [B/(B + D)] 55% [41% – 69%] 76% [62% – 87%] 0.043
  1. a These “false positives” may be a true error (the GSV user mis-interpreting another sign eg, a “no horses” sign for a “no dogs” sign) or may actually reflect a smokefree or dog control sign that was previously present when the GSV image was taken several years ago, but was not present in the field observations in 2016