"In estimation theory and statistics, the Cram\u00E9r\u2013Rao bound (CRB) or Cram\u00E9r\u2013Rao lower bound (CRLB), named in honor of Harald Cram\u00E9r and Calyampudi Radhakrishna Rao who were among the first to derive it, expresses a lower bound on the variance of estimators of a deterministic parameter."@en .