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

Table 2.

Differences in children’s cognitive levels by family structure 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 (N = 313) 94.32(10.12) 93.18(9.55) 95.49(10.57) 2.31(0.23)**
(4) Have elder sister (N = 379) 94.40(10.17) 95.73(10.47) 92.97(9.67) −2.76(−0.27)***
(5) Have younger brother (N = 204) 94.22(10.12) 94.70(9.18) 93.90(10.73) −0.8(−0.08)
(6) Have younger sister (N = 182) 95.17(9.86) 95.88(10.24) 94.63(9.58) −1.24(−0.13)
(7) Diff (2)-(1)(Cohen’s d) −1.07(0.10) −0.37(0.04) −2.78(0.26)*** −3.15(0.30)**
(8) Diff (3)-(1)(Cohen’s d) −1.57(−0.14)* −1.52(−0.14) −1.87(−0.18) −0.35(−0.03)
(9) Diff (4)-(1)(Cohen’s d) −1.50(−0.14)* 1.03(0.09) −4.40(−0.41)*** −5.42(0.50)***
(10) Diff (5)-(1)(Cohen’s d) −1.68(−0.15)* 0.00(0.00) −3.46(0.30)** −3.46(−0.31)*
(11) Diff (6)-(1)(Cohen’s d) −0.72(−0.07) 1.18(0.11) −2.72(−0.25)* −3.91(−0.36)*

Rows (6)-(11) 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