This study examined the intrarater and interrater reliability of the
Test of Gross Motor Development—3rd Edition (TGMD-3). Participants were
60 Finnish children aged between 3 and 9 years, divided into three
separate samples of 20. Two samples of 20 were used to examine the
intrarater reliability of two different assessors, and the third sample
of 20 was used to establish interrater reliability. Children’s TGMD-3
performances were video-recorded and later assessed using an intraclass
correlation coefficient, a kappa statistic, and a percent agreement
calculation. The intrarater reliability of the locomotor subtest, ball
skills subtest, and gross motor total score ranged from 0.69 to 0.77,
and percent agreement ranged from 87 to 91%. The interrater reliability
of the locomotor subtest, ball skills subtest, and gross motor total
score ranged from 0.56 to 0.64. Percent agreement of 83% was observed
for locomotor skills, ball skills, and total skills, respectively. Hop,
horizontal jump, and two-hand strike assessments showed the most
difference between the assessors. These results show acceptable
reliability for the TGMD-3 to analyze children’s gross motor skills.