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. 2025 Aug 6;25:2674. doi: 10.1186/s12889-025-23599-y

Table 3.

Differences in children’s cognitive levels by sibling interval and gender

1.All sample 2.Male (N = 674) mean (SD) 3.Female (N = 651) mean (SD) 4.Gender differences (Cohen’s d)
(1) Only child (N = 338) 95.90(11.58) 94.7(11.32) 97.36(11.77) 2.66(0.23)**
(2) Have siblings (N = 982) 94.82(10.10) 95.07(10.00) 94.57(10.21) −0.49(0.05)
(3) Have elder brother within 3 years (N = 72) 93.03(8.67) 93.07(9.13) 92.97(8.10) −0.1(−0.01)
(4) Have elder sister within 3 years (N = 119) 93.18(11.14) 95.55(12.10) 91.06(9.84) −4.49(−0.41)**
(5) Have younger brother within 3 years (N = 116) 94.35(10.25) 94.69(9.10) 94.14(10.97) −0.55(−0.05)
(6) Have younger sister within 3 years (N = 98) 94.34(9.70) 94.57(9.51) 94.38(9.90) −0.19(−0.02)
(7) Diff (3)-(1)(Cohen’s d) −2.87(−0.28)** −1.63(−0.15) −4.40(−0.39)* −2.77(−0.25)
(8) Diff (4)-(1)(Cohen’s d) −2.72(−0.24)** 0.85(0.07) −6.30(−0.56)*** −7.15(0.63)***
(9) Diff (5)-(1)(Cohen’s d) −1.54(−0.14) −0.01(0.00) −3.22(−0.28)* −3.21(−0.29)
(10) Diff (6)-(1)(Cohen’s d) −1.45(−0.13) −0.13(−0.01) −2.98(−0.26)* −2.85(−0.26)

Rows (7)-(10) show the differences between children in Multi-child families with different sibling structures and those who are only children. The last column shows the difference between girls and boys

* p value < 0.1 (marginally significant)

**p value < 0.05

***p value < 0.01