Hi People have been noting various transformations, depending on reversing or not the original. In essence many common transformations can be conceptualized as the original scores raised to various powers, with the powers being greater than or less than 1.
x^-1 = reciprocal 1/x x^~0 = logarithmic x^.5 = square root x^1 = original x^2 = ... I'm mostly used to thinking of these in terms of various non-linear relationships (powers < 1 compress upper end, powers > 1 expand upper end), but some of these will increase skewness and others will decrease it, depending on the direction of skew. Possible to experiment with them to observe effect. Perhaps also worth plotting some of the relationships you are interested in? Take care Jim Jim Clark Professor & Chair of Psychology 204-786-9757 4L41A -----Original Message----- From: Christopher Green [mailto:chri...@yorku.ca] Sent: Monday, November 11, 2013 5:31 PM To: Teaching in the Psychological Sciences (TIPS) Subject: Re: [tips] What to do with skewed data Michael, There are couple of standard ways to transform skewed data. Invert the data (subtract each datum from one greater than the highest value) so that the skew is positive. Then, Depending of the strength of the skew, do a square root or logarithmic transformation. Alternatively, don't invert it and take the reciprocal (1/x) of each datum). Chris ....... Christopher D Green Department of Psychology York University Toronto, ON M6C 1G4 chri...@yorku.ca http://www.yorku.ca/christo > On Nov 11, 2013, at 1:01 PM, Michael Britt <mich...@thepsychfiles.com> wrote: > > I did a survey which asked respondents how satisfied they are in their > current (romantic) relationship on a 1=10 point scale (where 10="very > satisfied). While there was some variation, not surprisingly, the results > are strongly negatively skewed. That makes sense - most people are probably > satisfied with their relationships or they would leave the other person (or > there's some form of cognitive dissonance going on, but that's not my > question. > > No matter how big the sample size (mine was 160 respondents) I assume you'll > always get a skewed distribution on a question like this so wouldn't I be > breaking the normalization assumption if I were to do correlations using > these results? I assume I could either do: a) do some kind of > transformation - but I've never done one before so I’m not familiar with it, > or b) recode the data into 3 categories (perhaps 1-5 is low satisfaction, 6-7 > is moderate and 8-10 is high) and do a chi-squre instead of a correlation. > > Any thoughts? Appreciate it. > > Michael > > Michael A. Britt, Ph.D. > mich...@thepsychfiles.com > http://www.ThePsychFiles.com > Twitter: @mbritt > > > --- > You are currently subscribed to tips as: chri...@yorku.ca. > To unsubscribe click here: > http://fsulist.frostburg.edu/u?id=430248.781165b5ef80a3cd2b14721caf62b > d92&n=T&l=tips&o=30023 or send a blank email to > leave-30023-430248.781165b5ef80a3cd2b14721caf62bd92@fsulist.frostburg. > edu > --- You are currently subscribed to tips as: j.cl...@uwinnipeg.ca. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13251.645f86b5cec4da0a56ffea7a891720c9&n=T&l=tips&o=30040 or send a blank email to leave-30040-13251.645f86b5cec4da0a56ffea7a89172...@fsulist.frostburg.edu --- You are currently subscribed to tips as: arch...@jab.org. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=30042 or send a blank email to leave-30042-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
