I recently gave a talk at an internal seminar on planned missingness for a group of developmental psychologists. The idea behind planned missingness is that you can shorten interview time or reduce costs, if you decide as a researcher not to administer all your instruments to everyone in your sample. When you either randomly assign people to receive a particular instrument, or do so by design (i.e. only collect bio-markers in an at-risk group), your missing data will either be Missing Completely At Random (MCAR) or Missing at Random (MAR).
In late august of 2011 I attended the Internet Survey Methodology Workshop. There were people from academia, official statistics and market research agencies there. One of the issues discussed there has had me thinking since: the topic of panel conditioning. Some people seem really worried that respondents in panel surveys start behaving or thinking differently because of repeated participation in a survey.
Panel conditioning is closely linked with the issue of ‘professional’ respondents.