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. 2019 Jun 25;14(6):e0218633. doi: 10.1371/journal.pone.0218633

Table 2. Summary subgroup analyses.

Outcome or Subgroup Title No. of studies No. of participants Statistical Method Effect Size (95% CI)

  1. Academic Performance Overall

 20 842 Std. Mean Difference (IV, Random, 95% CI) 0.28 (0.09 to 0.47)
1.1.1Preschool 6 122 Std. Mean Difference (IV, Random, 95% CI) 0.95 (0.35 to 1.55)
1.1.2 Primary School 13 666 Std. Mean Difference (IV, Random, 95% CI) 0.21 (0.09 to 0.34)
1.1.3 Middle School 1 63 Std. Mean Difference (IV, Random, 95% CI) -0.01 (-0.52 to 0.50)
1.2.1 Math 11 526 Std. Mean Difference (IV, Random, 95% CI) 0.08 (-0.09 to 0.26)
1.2.2 Reading 6 401 Std. Mean Difference (IV, Random, 95% CI) 0.04 (-0.16 to 0.24)
1.2.3 Spelling 4 341 Std. Mean Difference (IV, Random, 95% CI) 0.19 (-0.02 to 0.40)
1.2.4 Language 2 43 Std. Mean Difference (IV, Random, 95% CI) 1.07 (0.42 to 1.72)
1.2.5 Geography 1 19 Std. Mean Difference (IV, Random, 95% CI) 0.99 (0.02 to 1.96)
1.2.6 Science 3 94 Std. Mean Difference (IV, Random, 95% CI) 0.57 [-0.46, 1.61]
2. Executive Function 3 112 Std. Mean Difference (IV, Random, 95% CI) -0.04 (-0.41 to 0.34)
3. Fluid Intelligence 2 61 Mean Difference (IV, Random, 95% CI) 0.38 (-3.21 to 3.96)
4. Time on Task 7 541 Std. Mean Difference (IV, Random, 95% CI) 0.37 (0.06 to 0.68)
4.1 Primary School 6 480 Std. Mean Difference (IV, Random, 95% CI) 0.41 (0.03 to 0.79)
4.2 Middle School 1 61 Std. Mean Difference (IV, Random, 95% CI) 0.32 (-0.19 to 0.83)
5. Enjoyment 6 148 Std. Mean Difference (IV, Random, 95% CI) 0.68 (0.35 to 1.02)
5.1 Preschool 3 61 Std. Mean Difference (IV, Random, 95% CI) 0.85 (0.32 to 1.38)
5.2 Primary School 3 87 Std. Mean Difference (IV, Random, 95% CI) 0.58 (0.14 to 1.01)

Std: Standardized; IV: Inverse Variance; CI: Confidence Interval