Quantifying the role of trial study partner characteristics on informant reliability and data variability Lead Investigator: Josh Grill Institution : UC Irvine E-Mail : jgrill@uci.edu Proposal ID : 594 Proposal Description: The overall objective of the proposed research is to quantify the association between study partner characteristics and participant informant reliability along with bias and variance in observed cognitive measures. The specific aims of the project are as follows: Aim 1: To quantify patient characteristics and study partner contact by partner reliability Aim 1a: To compare participants and study partners, based on study partner reliability. Aim 1b: To quantify the level of contact between reliable and unreliable informants who do not co-reside with the patient participant. Aim 2: To assess the association between study partner criteria and informant reliability Aim 2a: To test whether study partner criteria, as defined by frequency of contact to the patient participant, is associated with informant reliability. Aim 2b: To test whether study partner criteria are associated with patient participant retention. Aim 2c: To determine whether study partner criteria are associated with variance in the change in informant-based outcome measures.