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. Author manuscript; available in PMC: 2013 Mar 13.
Published in final edited form as: Twin Res Hum Genet. 2010 Dec;13(6):550–558. doi: 10.1375/twin.13.6.550

Table 1.

The Mean Symptom Scores (Standard Deviations) of Problem Behaviors Among Boys and Girlsa: Teacher and Parental Ratings at Age 12

Teacher ratings Parental ratings
M SD M SD
Boys n = 1755 n = 1914
 Hyperactivity–impulsivity 0.89 0.78 0.81 0.55
 Aggressiveness 0.71 0.66 0.62 0.42
 Inattention 0.89 0.72 0.80 0.52
Girls n = 1864 n = 2023
 Hyperactivity–impulsivity 0.45 0.55 0.64 0.55
 Aggressiveness 0.49 0.55 0.54 0.39
 Inattention 0.48 0.55 0.57 0.46

Note:

a

p value of gender difference < .001 for all scores (based on t test adjusted for correlated twinship)

M: mean; SD: standard deviation