Editing Observational error (section)

==Surveys==
The term "observational error" is also sometimes used to refer to response errors and some other types of [[non-sampling error]].<ref name="Dodge"/> In survey-type situations, these errors can be mistakes in the collection of data, including both the incorrect recording of a response and the correct recording of a respondent's inaccurate response. These sources of non-sampling error are discussed in Salant and Dillman (1994) and Bland and Altman (1996).<ref>{{cite book |last1=Salant |first1=P. |first2=D. A. |last2=Dillman |title=How to conduct your survey |url=https://archive.org/details/howtoconductyour00sala |url-access=registration |location=New York |publisher=John Wiley & Sons |year=1994 |isbn=0-471-01273-4 }}</ref><ref>{{cite journal |last1=Bland |first1=J. Martin |first2=Douglas G. |last2=Altman |title=Statistics Notes: Measurement Error |journal=BMJ |volume=313 |issue=7059 |year=1996 |pages=744 |doi=10.1136/bmj.313.7059.744 |pmid=8819450 |pmc=2352101 }}</ref>

These errors can be random or systematic. Random errors are caused by unintended mistakes by respondents, interviewers and/or coders. Systematic error can occur if there is a systematic reaction of the respondents to the method used to formulate the survey question. Thus, the exact formulation of a survey question is crucial, since it affects the level of measurement error.<ref>{{cite book |last1=Saris |first1=W. E. |last2=Gallhofer |first2=I. N. |year=2014 |title=Design, Evaluation and Analysis of Questionnaires for Survey Research |edition=Second |location=Hoboken |publisher=Wiley |isbn=978-1-118-63461-5 }}</ref> Different tools are available for the researchers to help them decide about this exact formulation of their questions, for instance estimating the quality of a question using [[Multitrait-multimethod matrix|MTMM experiments]]. This information about the quality can also be used in order to [[Correction for attenuation|correct for measurement error]].<ref>DeCastellarnau, A. and Saris, W. E. (2014). A simple procedure to correct for measurement errors in survey research. European Social Survey Education Net (ESS EduNet). Available at:  [http://essedunet.nsd.uib.no/cms/topics/measurement/ http://essedunet.nsd.uib.no/cms/topics/measurement] {{Webarchive|url=https://web.archive.org/web/20190915033804/http://essedunet.nsd.uib.no/cms/topics/measurement |date=2019-09-15 }}</ref><ref>{{cite journal | last1 = Saris | first1 = W. E. | last2 = Revilla | first2 = M. | year = 2015 | title = Correction for measurement errors in survey research: necessary and possible | url =http://repositori.upf.edu/bitstream/10230/28341/1/RECSM-WP-031-Correction%20for%20measurement%20errors%20in%20survey%20research.pdf | journal = Social Indicators Research | volume =  127| issue = 3| pages =  1005–1020| doi = 10.1007/s11205-015-1002-x | hdl = 10230/28341 | s2cid = 146550566 | hdl-access = free }}</ref>