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Table 4 Parameter estimates for models of variance components, time, treatment (T1 and T2) and interaction (of time on treatment) main effects on the Perceived Stress Scale (PSS) group means.

From: An adaptogenic role for omega-3 fatty acids in stress; a randomised placebo controlled double blind intervention study (pilot) [ISRCTN22569553]

  Variance Components Time Main Effects Treatment Main Effects Interaction Main Effects
Fixed effects Coeff. (S.E.) Coeff. (S.E.) Coeff. (S.E.) Coeff. (S.E.)
β Constant 17.639 (0.533) 18.444 (0.597) 16.479 (0.598) 15.836 (0.614)
Time   -1.999 (0.669)* -2.223 (0.665)* -0.500 (0.770)
T2    6.958 (1.241)* 8.092 (1.441)*
T3    5.372 (1.164)* 8.101 (1.365)*
T2 × time     -2.786 (1.679)
T3 × time     -6.059 (1.554)*
Random effects     
Subject level residual variance 15.498 (4.260) 16.639 (4.200) 8.226 (3.063) 9.867 (2.956)
Time level residual variance 18.496 (3.115) 16.599 (2.801) 16.721 (2.801) 13.930 (2.334)
-2 log likelihood 1020.264 1011.772 974.964 960.204
  1. * Denotes significance (Wald statistic ≥ 1.96, where p ≤ 0.05). Note: T2 = olive oil group, T3 = fish oil group, Coeff. = coefficient, S.E. = standard error, -2 log likelihood statistic = -2LL.