Statistical Analysis
aphasia
Although the POLAR trial was not designed to investigate therapy efficacy as such, we first assessed therapy-induced change in naming to confirm the expected response to established SLTs. To this end, naming performance on the PNT 1 week, 1 month, and 6 months posttherapy was compared to baseline performance. Paired Second, we investigated the relationship between five prognostic factors and treated language recovery: Western Aphasia Battery–Aphasia Quotient (WAB-AQ) as a measure of aphasia severity, age, TPO in months, education in years, and WAIS Matrix Reasoning score as a measure of cognitive reserve. Relationships across independent variables (i.e., WAB-AQ, age, TPO, education, and WAIS Matrix Reasoning) and between independent variables and naming performance at baseline, as well as long-term change in naming performance (1 week, 1 month, and 6 months posttherapy), were inspected using Pearson's or Spearman's correlation as appropriate. This analysis served to characterize the relationship across variables. For this reason, we report the results without correction for multiple comparisons.Third, we constructed general linear models (GLMs) to test the association between predictor variables and therapy-induced naming gains. Consistent with recent findings indicating that prognostic factors for immediate therapy response may differ from those of long-term retention of therapeutic gains (Model accuracy was estimated using a leave-one-out cross-validation (LOOCV). One participant was set aside, and the model was trained on behavioral data from All statistical analyses were carried out using R software (Version 3.6.0). GLMs were constructed using the 