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Table 2 Number and percent of non-right-handers (NRH) and right handers (RH) by sample and sex for four handedness direction indicators

From: Prevalence and heritability of handedness in a Hong Kong Chinese twin and singleton sample

 TwinsSingletonsTotal
Handedness DirectionMale
n (%)
Female
n (%)
χ2(df = 1)Male
n (%)
Female
n (%)
χ2(df = 1)Twins
n (%)
Singletons
n (%)
χ2(df = 1)
Writing hand
 NRH17 (9.1%)14 (7.1%)0.5119 (8.6%)14 (6.9%)0.4631 (8.1%)33 (7.8%)0.02
 RH170 (90.9%)183 (92.9%) 201 (91.4%)190 (93.1%) 353 (91.9%)391 (92.2%) 
Drawing hand
 NRH26 (13.9%)21 (10.7%)0.9427 (12.3%)29 (14.2%)0.3547 (12.2%)56 (13.2%)0.17
 RH161 (86.1%)176 (89.3%) 193 (87.7%)175 (85.8%) 337 (87.8%)368 (86.8%) 
EHI2
 NRH13 (7.0%)12 (6.1%)0.1220 (9.1%)16 (7.8%)0.2125 (6.5%)36 (8.5%)1.13
 RH174 (93.0%)185 (93.9%) 200 (90.9%)188 (92.2%) 359 (93.5%)388 (91.5%) 
PegQ2
 NRH23 (12.1%)29 (14.2%)0.3840 (18.1%)25 (12.2%)2.8752 (13.2%)65 (15.3%)0.71
 RH167 (87.9%)175 (85.8%) 181 (81.9%)180 (87.8%) 342 (86.8%)361 (84.7%) 
  1. 1) For the binary classification of ‘writing hand’ and ‘drawing hand’, NRH includes both left-hand preference and no preference
  2. 2) EHI2 and PegQ2 are the binary classification of EHI and PegQ scores respectively, using zero as the cutoff point. NRH refers to those who scored less or equal to zero. There are 4 participants (including 1 twin and 3 singletons) who scored exactly zero on EHI