A

B

C

D

And

Sample size

200

198

198

156

200

Get to the bottom of the grades

4.11 (3.55 - 4.24)

4.11 (3.54 - 4.30)

3.41 (3.30 - 3.55)

4.23 (4.06 - 5.02)

4.08 (3.40 - 4.23)

Measured results

3.56 (3.43 - 4.09)

4.00 (3.41 - 4.18)

3.39 (3.28 - 3.50)

4.03 (3.48 - 4.27)

3.54 (3.38 - 4.10)

With

−9.812

−8.647

−4.146

−9.159

−8.694

P

<0.05

<0.05

<0.05

<0.05

<0.05