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PAPER LME REPLICATION -- mergeNaive (days 0-13)
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model: behavior ~ stim + day + stim:day + (1|rat)   [stim: Electrode-Box-B2=1 vs Electrode-Box-A2=0]
behavior = successful reaches (COUNT per session)
N = 11 rats, 138 sessions   (day raw; day 0 = paper "Day 1")
day coverage: stim(B2) 0..13, control(A2) 0..13
(Equal day coverage -- the stim:day interaction over this window is NOT
 confounded by the full-range coverage imbalance.)

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FULL MODEL SUMMARY -- fitlme: behavior ~ stim + day + stim:day + (1|rat)
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Linear mixed-effects model fit by ML

Model information:
    Number of observations             138
    Fixed effects coefficients           4
    Random effects coefficients         11
    Covariance parameters                2

Formula:
    behavior ~ 1 + day*stim + (1 | rat)

Model fit statistics:
    AIC       BIC       LogLikelihood    Deviance
    1164.9    1182.4    -576.44          1152.9  

Fixed effects coefficients (95% CIs):
    Name                   Estimate    SE         tStat     DF     pValue    
    {'(Intercept)'}        16.254       4.2865     3.792    134    0.00022519
    {'day'        }        6.4041      0.42677    15.006    134    1.7662e-30
    {'stim'       }        8.9845       7.0391    1.2764    134       0.20403
    {'day:stim'   }        1.7992      0.67672    2.6587    134      0.008801


    Lower      Upper 
     7.7764    24.732
     5.5601    7.2482
    -4.9377    22.907
    0.46073    3.1376

Random effects covariance parameters (95% CIs):
Group: rat (11 Levels)
    Name1                  Name2                  Type           Estimate
    {'(Intercept)'}        {'(Intercept)'}        {'std'}        8.1481  


    Lower     Upper 
    4.7633    13.938

Group: Error
    Name               Estimate    Lower     Upper 
    {'Res Std'}        14.825      13.109    16.766



effect                     t (df)        F (df1)       p
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stim x day (interaction)   t(134)=  2.66  F(1)=   7.068  p=0.008801
day (learning)             t(134)= 15.01  F(1)= 225.182  p=1.766e-30
stim (main, Day 1)         t(134)=  1.28  F(1)=   1.629  p=0.204
interaction 95% CI: [+0.46, +3.14]

INTERPRETATION
  - stim x day interaction: SIGNIFICANT (p=0.0088, slope diff=+1.80) -> tDCS (Box-B2) improves FASTER -- benefit accumulates over training.
  - stim main effect on Day 1 (our day 0): n.s. (p=0.2040) -> groups are comparable on Day 1.

Paper (N=24): interaction t(227)=2.68, F(1)=7.12, p=0.008; day t(227)=9.64,
  F(1)=267.64, p=1.2e-18; stim t(227)=0.23, F(1)=0.053, p=0.81.