Table 1.
Results of nested ANCOVA [body mass as covariate, line (replicate line 1–8) as random effect nested within linetype (C versus HR): SAS Procedure mixed] comparing mice from C and HR lines when housed either without or with access to wheels for 8 weeks (data from Kelly et al. 2006)
| Trait | N | ln maximum likelihood | −2 × ln maximum likelihood | Likelihood ratio testa, P | P for HR versus. Cb | P for MMb | P for Revs. in final 6 days | −2 × ln restricted maximum likelihood; first iteration | −2 × ln restricted maximum likelihood; last iteration | Line likelihood ratio testc | P for linec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No wheel | |||||||||||
| Femur | 40 | 0.1055+ | 0.0050− | −232.75 | −238.00 | 5.24 | 0.0220 | ||||
| Tibiafibula | 39 | 0.0256+ | 0.0885− | −236.70 | −244.56 | 7.86 | 0.0050 | ||||
| Foot (all bones) | 40 | 0.0012+ | 0.0438+ | −251.00 | −251.36 | 0.37 | 0.5446 | ||||
| Wheel | |||||||||||
| Femur | 39 | 118.26 | −236.52 | 0.726, 0.3942 | 0.8183+ | 0.8567− | 0.4499+ | −180.66 | −183.35 | 2.69 | 0.1011 |
| 39 | 117.90 | −235.79 | 0.5213+ | 0.9712− | −205.89 | −208.98 | 3.10 | 0.0785 | |||
| Tibiafibula | 39 | 125.85 | −251.70 | 1.835, 0.1755 | 0.2492+ | 0.6328− | 0.2456+ | −195.63 | −195.94 | 0.30 | 0.5814 |
| 39 | 124.93 | −249.86 | 0.0702+ | 0.8377− | −220.37 | −221.18 | 0.81 | 0.3681 | |||
| Foot (all bones) | 40 | 127.43 | −254.87 | 4.270, 0.0388 | 0.2170+ | 0.7043+ | 0.0549+ | −199.07 | −199.08 | 0.00 | 0.9436 |
| 40 | 125.30 | −250.60 | 0.0248+ | 0.5255+ | −221.60 | −221.83 | 0.22 | 0.6375 |
aTwice the difference in ln maximum likelihood is distributed as a χ2 with 1 df, i.e., 3.841 for P = 0.05. Values larger than this indicate that the model including amount of running during final week as a covariate (full model) fits the data significantly better than a model that does not include this covariate (reduced model).
b P-values ≤ 0.05 (unadjusted, two-tailed) are noted in bold. Signs following P values indicate direction of effect based on the partial regression from the mixed model: + indicates HR lines > C, and MM > non-MM.
cIn each one-way ANCOVA, to determine if significant variation among replicate lines was present, the −2 ln restricted maximum likelihoods of the initial and last iteration evaluations within each ANCOVA were examined. The difference in −2 ln REMLs can be compared with a χ2 distribution with 1 df, for which the critical value for P = 0.05 is 3.841.