Estimating the Mean of Observations from a Wide-Sense Stationary Autoregressive Sequence

Abstract

This study concerns the relative efficiency of the least-squares estimator of the mean of a covariance stationary sequence that has a constant mean and an autoregressive representation of order p. Our results augment those in [2]. The results in Section 1 include for any positive integer p the variance of the LSE, the BLUE in terms of autoregressive coefficients, the variance of the BLUE and the range of applications of Ylvisaker's theorem [7] regarding a lower bound on relative efficiency. For second-order schemes it also includes bounds on parameter values for relative efficiency >0.80. Graphical results for the first-order scheme in Section 2 add to the detailed study made in [2] and imply that the relative desirability of the LSE should be based on variance as well as relative efficiency considerations.