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Mean Age at Menarche by Zygosity and Cotwin Control Group
| Group | M | SD | n |
|---|---|---|---|
| MZ concord no step | 13.02 | 1.40 | 528 |
| MZ discord no step | 12.89 | 1.17 | 36 |
| MZ discord step | 12.61 | 1.52 | 33 |
| MZ concord step | 12.92 | 1.29 | 25 |
| DZ concord no step | 13.14 | 1.46 | 583 |
| DZ discord no step | 12.16 | 1.62 | 25 |
| DZ discord step | 12.41 | 1.30 | 29 |
| DZ concord step | 12.16 | 1.37 | 25 |
Note. MZ = monozygotic; DZ = dizygotic; concord = concordant; discord = discordant; step = stepfather.
