>Stephen Black wrote: > >> I also side with Jim Clark on this one. This is a debate that >> split experimental psychology some years ago (Can you say "John >> Gaito"?). The opinion I arrived at was that levels of measurement >> is one of those topics that we like to torture students with but >> has no real utility (another example is the negative/positive >> reinforcement distinction). Even though the t-test is supposed >> only to be used with data which satisfies a rather restrictive >> set of assumptions, it turns out to be "robust" when its >> assumptions are violated, so it can be happily (and justifiably) >> used in lots of other cases. > > Is it fair to say that the current consensus is that t-tests and >means are useful for what we have always thought of as ordinally scaled data >(for example, code numbers assigned to points along a "strongly agree" to >"strongly disagree" variable)? I personally still feel moral anxiety when I >do that kind of thing <grin>, and I'd love to relieve my feelings of guilt. > >Paul Smith >Alverno College >Milwaukee
If that scale is well-constructed, it _is_ an interval scale (or awfully close to one). Measurement issues are beyond my area of expertise, but as I understand it, if you only label the endpoints, subjects tend to treat it as an interval scale. If you carefully label each code number (and can show that subjects perceive each label as about equally far from its neighbors) then it's also an interval scale. On the other hand, if your labels are something like, "never," "almost never," "pretty often," and "always," you'll have a hard time arguing that that's an interval scale. Charlotte -- ====================================================== Charlotte F. Manly, Ph.D. | Psychological & Brain Sciences Assistant Professor | 317 Life Sciences Bldg ph: (502) 852-8162 | University of Louisville fax: (502) 852-8904 | Louisville, KY 40292 [EMAIL PROTECTED] http://www.louisville.edu/a-s/psychology/ http://www.louisville.edu/~cfmanl01 --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
