```Date: Thu, 4 Dec 1997 20:14:12 GMT Reply-To: Richard F Ulrich Sender: "SPSSX(r) Discussion" From: Richard F Ulrich Organization: University of Pittsburgh Subject: Re: correlation coefficient William Dudley (wdudley@SPH.EMORY.EDU) wrote: : >At 13:59 04/12/97 +0000, Safa Gurcan wrote: : >>Hi, : >>Hi, : >>I have 30 chicken, each chicken has repeated measures(not equal) and : >>2 variables (live weight and egg weight). In general total n size is : >>392. I want to calculate to correlation coefficient between 2 : >>variables. If i calculate the arithmetic mean of 2 variables for each : >>chicken, n size will be reduced to 30. I think that if i do this : >>process a lot of information will be lost. << snip, details; recommendations >> : I wonder what other readers would do with these data? If there is just one live-weight per chicken, then there is only the possibility of a "between-chicken" sort of correlation or regression. For any statistic between-chicken, the n=30; it is not "reduced" to 30, because there were never more than 30 chickens. The simple way to compute is to start with the average egg-weight for each chicken, though it is conceivable to do weighting by the n or the standard error. Is there homogeneity among the egg-weights, across chickens? - you could construct an ANOVA between chickens, and that would make further use of "within-chicken" data. If there are within-chicken live-weights, then you could have within-chicken regressions, between live-weight and egg-weight. If these are not heterogeneous, then it would be fair to average them. Rich Ulrich, biostatistician wpilib+@pitt.edu http://www.pitt.edu/~wpilib/index.html Univ. of Pittsburgh ```

Back to: Top of message | Previous page | Main SPSSX-L page