Objective: Cognitive dysfunction in clinical trials is often assessed with various instruments including the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog), the Mini-Mental Status Examination (MMSE), or the Clinical Dementia Rating scale-Sum of Boxes (CDR-SOB). The use of different measures across trials and centers makes comparing results difficult. However, modern psychometric techniques allow for different measures to be compared on the same metric. This study aimed to produce a simple chart that shows how raw scores on these three important measures correspond to each other. Method: Data from 1709 participants (768 female) from the Alzheimer's Disease Neuroimaging Initiative were analyzed. Participants were an average of 73.70 years old (SD = 7.18 years), predominantly identified as White (92%), and represented a range of cognitive impairment (24% cognitively normal, 6% subjective memory complaints, 51% mild cognitive impairment, 19% Alzheimer's disease). Using item response theory-based statistics, we analyzed how raw scores on each measure, the ADAS-Cog, the MMSE, and the CDR-SOB, correspond. This psychometric technique can provide statistical bridges between these three measures of cognitive dysfunction. Results: Results indicated multiple inflections in CDR-SOB and ADAS-Cog scores within a given MMSE score, suggesting that the CDR-SOB and ADAS-Cog are more precise in measuring severity of cognitive dysfunction than the MMSE. Relationships between specific raw scores among the three measures were detailed in a useful table. Conclusion: This study shows how scores on these three commonly used measures of cognitive dysfunction correspond to each other, which is very useful information for clinical researchers.