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Table 5 Model fitting results of the means model on triplet BW

From: Birth weight in a large series of triplets

step Model Nparameters -2LL df to model Χ 2 Δ df p
1 Full model 25 576.10 1194     
2 a. Equal mean MZ pairs within MZ and DZ trios 22 577.11 1197 1 1.01 3 0.80
  b. Equal var MZ pairs within MZ and DZ trios 21 579.62 1198 2a 2.51 1 0.11
  c. Equal cov MZ pairs within MZ and DZ trios 20 581.32 1199 2b 1.70 1 0.19
3 a. Equal mean DZ/TZ 17 597.89 1202 2c 16.57 3 '0.00
  b. Equal var DZ/TZ 19 584.16 1200 2c 2.84 1 0.09
  c. Equal cov DZ/TZ 18 585.71 1201 3b 1.01 2 0.31
4 a. Equal mean within MZ 16 591.32 1203 3c 5.61 2 0.06
  b. Equal mean within DZ 14 592.24 1205 4a 0.92 2 0.63
  c. Equal mean within TZ 12 621.31 1207 4b 29.07 2 0.00
5 a. Effect GA2 = 0 13 594.73 1206 4b 2.49 1 0.11
  b. Effect GA = 0 12 1013.26 1207 5a 418.53 1 0.00
  c. Effect sex = 0 12 631.42 1207 5a 36.69 1 0.00
  d. Effect alcohol = 0 12 594.84 1207 5a 0.11 1 0.74
  e. Effect smoking = 0 11 605.74 1208 5d 10.9 1 0.00
  1. MZ = monozygotic; DZ = dizygotic; TZ = trizygotic; GA = gestational age. The best fitting model is printed in bold font.