Table 6 Multiple regression analysis between the University Selection Test (PSU) (mean language + mathematics), language PSU and mathematics PSU scores (dependent variables) and the most relevant parameters (independent variables).

From: Brain structural parameters correlate with University Selection Test outcomes in Chilean high school graduates

Parameter

Estimate

Standard Error

of Estimate

T for H0:

Parameter = 0

p >|T|

PSU score (mean language + mathematics)

Intercept

−291.5

139.4

−2.09

.0393

IA (Ref: Grades IV + V)

Grade I + II

239.3

26.9

8.87

.0001

Grade III

49.8

26.0

1.92

.0586

GMV

0.59

0.15

3.90

.0002

rIFG

106.9

37.4

2.86

.0053

SES (Ref: Medium)

High SES

16.6

20.1

0.83

.4097

Low SES

44.6

18.4

2.41

.0178

Sex (Ref: males)

Females

−27.8

19.1

1.45

.1505

Language PSU score

Intercept

−251.3

148.0

−1.70

.0930

IA (Ref: Grades IV + V)

Grade I + II

235.9

28.6

8.24

.0001

Grade III

68.7

27.6

2.49

.0146

GMV

0.64

0.16

4.03

.0001

SES (Ref: Medium)

High SES

26.9

21.3

1.26

.2113

Low SES

−41.5

19.6

−2.12

.0368

rIFG

71.0

39.7

1.79

.0770

Sex (Ref: males)

Females

−35.8

20.3

1.76

.0817

Mathematics PSU score

Intercept

−321.8

175.5

−1.83

.0699

IA (Ref: Grades IV + V)

Grade I + II

238.8

32.8

7.27

.0001

Grade III

27.5

32.0

0.86

.3912

rIFG

142.9

47.5

3.00

.0034

GMV

0.52

0.19

2.75

.0071

SES (Ref: Medium)

High SES

6.08

25.5

0.24

.8127

Low SES

−49.1

23.2

−2.12

.0370

Sex (Ref: males)

Females

−18.3

24.1

0.76

.4494

  1. Model R2 = .811; Root MSE (Root mean squared error, standard deviation of the dependent variable PSU) = 71.4949; Model F Value = 55.76, p < .0001.
  2. Model R2 = .770; Root MSE (Root mean squared error, standard deviation of the dependent variable language PSU) = 75.9123; Model F Value = 43.61, p < .0001.
  3. Model R2 = .750; Root MSE (Root mean squared error, standard deviation of the dependent variable mathematics PSU) = 90.9008; Model F Value = 39.52, p < .0001.
  4. IA, intellectual ability; IA grades: Grade I, superior; Grade II, above average; Grade III, average; Grade IV, below average; Grade V, intellectually defective. GMV, gray matter volume. rIFG, right inferior frontal gyrus thickness. SES, socio-economic status. The initial regressors (independent variables considered in the statistical model) considered for the forward stepwise selection method were IA, SES, sex, brain segmentation without ventricles, GMV, brainstem, rIFG, right cerebellum cortex, left cerebellum cortex.
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