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From |
"David Radwin" <dradwin@mprinc.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: RE: Mean test in a Likert Scale |

Date |
Fri, 31 Aug 2012 09:32:31 -0700 (PDT) |

Rob, It may be the case that not labeling the middle points of a scale, as in your first example, justifies the assumption of equal spacing (deltas). But the literature suggests that verbally labeling all points on a scale, as in your second example, leads to more reliable measurement. See, for example: Alwin DF, Krosnick JA. 1991. The reliability of survey attitude measurement: The influence of question and respondent attributes. Sociol. Methods Res. 20:139-81. http://deepblue.lib.umich.edu/bitstream/2027.42/68969/2/10.1177_0049124191 020001005.pdf David -- David Radwin Senior Research Associate MPR Associates, Inc. 2150 Shattuck Ave., Suite 800 Berkeley, CA 94704 Phone: 510-849-4942 Fax: 510-849-0794 www.mprinc.com > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu [mailto:owner- > statalist@hsphsun2.harvard.edu] On Behalf Of Rob Ploutz-Snyder > Sent: Friday, August 31, 2012 9:13 AM > To: statalist@hsphsun2.harvard.edu > Subject: Re: st: RE: Mean test in a Likert Scale > > My 2 cents...when designing these sorts of instruments... > > I was trained that a true likert scale doesn't label each of the > points in the 5-point (or other) scale, but instead has only TWO > labels at each extreme. For example: > > I like Statalist.............. Completely Disagree 1 2 3 4 > 5 Completely Agree > > This is in CONTRAST to a scale that would label each and every point > (sometimes called "likert-type" or "modified-likert") for example: > > 1=completely disagree > 2=disagree > 3=neutral > 4=agree > 5=completely agree > > With true likert scales, while still not continuous in scale, the > distance between each category in a true likert scale is not > subjective. The delta between "1" and "2" is the same as the delta > between "2" and "3" etc. and it is assumed that survey respondents > can appreciate this. The same cannot be assumed about the difference > between "completely disagree" and "disagree" being equal to the delta > between "disagree" and "neutral." > > So in that way, a true-likert scale removes some of the subjectivity > on the deltas and seems to achieve a more proper ordinal scale as > opposed to purely categorical. > > Still doesn't justify using parametric statistical techniques... > However, most well-vetted Sociology or Psychological instruments are > designed to use multiple questions that, together, are used to measure > a particular construct. Social scientists don't usually intend to > compare responses on single questions, but instead ask many questions > that cluster together, often verified by exploratory or confirmatory > factor analysis, where "factor scores" are then created to capture the > overall construct of interest. These factor scores can be derived by > different methods, the simplest being a mean of the items that cluster > together, but usually by more sophisticated regression-based methods > that weigh each item according to how well it correlates with the > overall factor structure. These factor scores are continuously > scaled, unlike the individual items that were used to derive them, and > it is these factor scores that are often analyzed by various > parametric statistical techniques. > > Whether or not the factor scores are normally distributed in the > population (the real question) is dependent on the particulars of each > research study, but I don't categorically deny that the assumption is > invalid. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: RE: Mean test in a Likert Scale***From:*Rob Ploutz-Snyder <robploutzsnyder@gmail.com>

**Re: st: RE: Mean test in a Likert Scale***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**Re: st: RE: Mean test in a Likert Scale***From:*Leonor Saravia <lmisaravia@gmail.com>

**Re: st: RE: Mean test in a Likert Scale***From:*Nick Cox <njcoxstata@gmail.com>

**RE: st: RE: Mean test in a Likert Scale***From:*"David Radwin" <dradwin@mprinc.com>

**Re: st: RE: Mean test in a Likert Scale***From:*Rob Ploutz-Snyder <robploutzsnyder@gmail.com>

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