Tarkkonen's rho - Reliability or Validity Kindly advise what the value we obtain for Tarkkonen's rho tells us about - reliability or validity of the data being measured.
Thank you
 A: Tarkkonen's $\rho_{uu}$ is a measure of reliability, but $\rho_{uy}$ is defined as a predictive validity parameter in the original article (Tarkkonen & Vehkalahti, 2005). This article discusses both reliability and validity within Tarkkonen's proposed framework based on a measurement model. It appears to be applicable to structural validity as well. I'm not sure it belongs wholly to either class. Nonetheless, Vehkalahti, Puntanen, and Tarkkonen (2007; see also 2006) refer to Tarkkonen's rho as a "general estimator of reliability", so maybe that would be the safest bet if one had to choose.

References
· Tarkkonen, L., & Vehkalahti, K. (2005). Measurement errors in multivariate measurement scales. Journal of Multivariate Analysis, 96(1), 172–189. Retrieved from http://www.sciencedirect.com/science/article/pii/S0047259X04001800.
· Vehkalahti, K., Puntanen, S., & Tarkkonen, L. (2006). Estimation of reliability: A better alternative for Cronbach's alpha. Reports on Mathematics, 430, Department of Mathematics and Statistics, University of Helsinki, Finland. Retrieved from https://wiki.helsinki.fi/download/attachments/33885362/Preprint430.pdf.
· Vehkalahti, K., Puntanen, S., & Tarkkonen, L. (2007). Effects of measurement errors in predictor selection of linear regression model. Computational Statistics & Data Analysis, 52(2), 1183–1195. Retrieved from https://wiki.helsinki.fi/download/attachments/33885362/Preprint439.pdf.
· Vehkalahti, K., Puntanen, S., & Tarkkonen, L. (2009). Implications of dimensionality on measurement reliability. In B. Schipp & W. Kräer (Eds.), Statistical inference, econometric analysis and matrix algebra (pp. 143–160). Heidelberg: Physica Verlag.
