<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><blockquote type="cite"><div><font class="Apple-style-span" color="#000000">Lunedi 15 Giugno, ore 15</font></div><div><font class="Apple-style-span" color="#000000">Dipartimento di Economia, Finanza e Statistica, Aula 201</font></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Gill Sans"><font class="Apple-style-span" color="#000000">Università degli Studi di Perugia</font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal 'Gill Sans'; min-height: 14px; "><font class="Apple-style-span" color="#000000"><br></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font style="font: 12.0px Gill Sans"><font class="Apple-style-span" color="#000000">.: Advances in the use of auxiliary variables and calibration :.<font class="Apple-style-span" color="#000000"></font></font></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">.: Carl-Erik Särndal, University of Montreal :.</div></div><div><font class="Apple-style-span" color="#000000"><br></font></div><div>Abstract<i></i></div><div><i>Calibration</i><span style="font-style:normal"> is the name of a highly general approach to estimation in sample surveys. It has attracted considerable attention in recent years. The calibration approach is a part of statistical estimation theory, concerned in particular with inference for finite populations. The term calibration began be used around 1992. Earlier methods with particular names are now special cases of calibration, for example, post-stratification, raking ratio and others. Another familiar procedure, generalized regression (GREG) estimation, has features akin to calibration. When one wants to explain what calibration is all about, three familiar concepts enter immediately into consideration: auxiliary information, weighting, and consistency. The relationships are briefly as follows: <u>Calibration and auxiliary information</u>: The prime objective of calibration is usually (but not always) to improve on some more elementary form of estimation, via the use of (powerful) auxiliary information. To reduce variance or to reduce bias are objectives of this kind. Quite appropriately, calibration is sometimes described as a systematic approach to the use of auxiliary information in sample surveys. Calibration may not be unique in this regard, but it does offer a wide and easily understood conceptual framework for the use of auxiliary information. <u>Calibration and weighting</u>: Calibration uses <i>weighting</i><span style="font-style:normal"> to produce estimates of finite population parameters such as totals, functions of totals, quantiles, and others. Computationally, calibration delivers a set of </span><i>calibrated weights</i><span style="font-style:normal">; these weights are used to compute linearly weighted sums (estimates). To attach weights to observed variable values is an old, intuitively appealing idea; it is extensively used in national statistical agencies producing information for the country. One may argue that linear weighting poses an unnecessarily restrictive limitation; good estimates can be constructed by other than linear forms. Be that as it may, the word “weighting” is frequent in the literature, in various constellations, such as regression weighting, repeated weighting, and others. <u>Calibration and consistency</u>: The word “calibration” suggests “conformity with a standard”, or “conformity with reliable sources”, similarly as when the word is used in physics or engineering to address a need to calibrate a sensitive instrument or piece of equipment to a reliable standard. A similar connotation lies in the French term “calage”. “Consistency” refers more specifically to a desired agreement, for “the control variables”, with known (non-random) quantities or with “well estimated” (random) quantities. This consistency is to some degree a user-driven perspective: The statistical agency reassures the user by demonstrating agreement with other aggregate data on the same variables. Calibration on <i>known</i><span style="font-style:normal"> population totals is too narrow an aspect of this consistency; when the objective is to reduce nonresponse bias, calibration to </span><i>estimated</i><span style="font-style:normal"> quantities is equally important.<span style="mso-spacerun: yes"> Calibration has been used both for design-based inference and for model-based inference in sample surveys. My presentation focuses on the design-based perspective. It is in my opinion when we leave the pure conditions - i.e. there is no nonresponse, no frame errors or other non-sampling errors, there is only <i>one</i><span style="font-style:normal"> target variable y - and address more realistic survey conditions that the calibration approach offers its greatest future potential. My presentation will<span style="mso-spacerun: yes"> </span>review some of the recent literature on calibration for those more complex situations.</span></span></span></span></span></div><p class="MsoNormal" style="text-align:justify"><o:p></o:p></p> <!--EndFragment--> <div><p class="MsoNormal" style="text-align:justify"><o:p></o:p></p> <!--EndFragment--> </div><div>Cordiali saluti</div><div><br></div><div> <span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-variant: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-variant: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-variant: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div><font class="Apple-style-span" color="#000000">M. Giovanna Ranalli</font></div><div><font class="Apple-style-span" color="#000000"><br class="khtml-block-placeholder"></font></div><div><font class="Apple-style-span" color="#000000">~ Dipartimento di Economia, Finanza e Statistica</font></div><div><font class="Apple-style-span" color="#000000">~ Sezione di Statistica</font></div><div><font class="Apple-style-span" color="#000000">~ Via Pascoli</font></div><div><font class="Apple-style-span" color="#000000">~ 06123 Perugia - Italy</font></div><div><font class="Apple-style-span" color="#000000"><br class="khtml-block-placeholder"></font></div><div><font class="Apple-style-span" color="#000000">~ Tel +39 075 5855939</font></div><div><font class="Apple-style-span" color="#000000">~ Fax +39 075 5855950</font></div><div><font class="Apple-style-span" color="#000000">~ url: <a href="http://www.stat.unipg.it/~giovanna">www.stat.unipg.it/~giovanna</a></font></div></span></span></span></span></div><br></blockquote></div><br></body></html>