On 27 Jan 2004 01:59:46 -0800, [EMAIL PROTECTED] (Iain Toft) wrote: > I'm no stats expert but would like to solve the following problem. > > Given two sets of scores... > > S1 = [38.37388112, 38.37471969, 38.40682618, 38.37863674, ..., > 38.39506964] > S2 = [22.40683282, 22.23267916, 22.08881316, 24.96633041, ..., > 21.8635192] > > I'd like some statistical evidence to show the scores attained in S2 > are inferior to those in S1. I can show the mean,min,max,stdev but > would like something with a little more clout.
The Subject: line asks, "is this a t-test problem." It would seem likely to be, if the numbers were not weird. If one set of numbers ranges from 38.4- to 38.4+ while the other ranges by 3 points or more, then the *assumption* seems pretty invalid, that you should imagine the same process as generating both. Perhaps more should be said, in order to make the problem seem "reasonable". Then, you go to say that they are *paired* scores. No explanation is offered for why the one set is so near to a constant. If they are pairs, and one score is nearly fixed, is it better (more reasonable) to ask whether the *difference* is has some properties? - the difference is a very popular starting point when scores are properly assorted by pairs. Suppose the numbers lump up in a few places -- That is the prospect by which I can imagine that the two examples could overlap. When the *other* group is bigger, the pairs of scores are merely reversed, and intermediate scores do not occur. You get a *robust* test by asking the simple question, Which one is higher? If the starting values are indicator, then the one sample is higher for all 50 values. Look more widely for examples, if you want to see what a t-test is ordinarily used for, and what it is best for. Those data are not a good example. I find that google has pretty good success when < FAQ tutorial > are combined with broader topics, such as "paired t test". -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html "Taxes are the price we pay for civilization." . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
