MAPT and early-onset autosomal dominant Alzheimer disease: Negatively correlated measurements are encountered in numerous applications, for example in dementia research, where ratios of cerebrospinal fluid (CSF) biomarkers are used for the early diagnosis of Alzheimer’s disease (AD).23 Importantly, measurements of the widely employed amyloid-β 42 protein and total tau protein biomarkers are known to exhibit a negative correlation.24 In recent publications, the Gaussian regression model has been used for modeling ratios of CSF biomarkers (e.g., Xu et al).