B

C

D

Sample size

198

198

158

Get to the bottom of the grades

202.42 ± 33.46

207.97 ± 31.56

193.98 ± 30.68

Measured results

203.18 ± 31.85

208.16 ± 2.28

200 ± 31.02

T

1.036

−0.279

8.078

P

0.301

0.780

<0.05