I want to find the relationship between two variables- one is a population and other the site of its origin. I have only three sites of origin and have to plot the mean of the samples from that population. Probably the correlation analysis could not be performed using only three samples ( as it would not give significant results at any cost due to very small sample size). It is not possible for me to increase the no of sites. If I use individual sample from each population, I must be practicing pseudoreplication. How can I use my this data to find the relationship between my variables. Is there any alternative method to do this. Is performing correlation on such a small data set reasonable. I got r value of as high as 0.9 but with non significant p value. I know the reason is small sample size but cannot increase it. What should I do?
Instead of treating each site as the unit of analysis and reducing a rich dataset to only 3 points, you can use an approach like mixed-effects modeling to treat each individual measurement of phenotypic plasticity as the unit of analysis. Because latitude is the true effect of interest rather than site, consider a model specification in which there is a fixed effect of latitude and a random intercept by site (the latter of which accounts for the fact that observations are correlated within a site – this is the pseudoreplication problem that you were rightly concerned about). Make sure to put some thought into whether your scientific hypothesis warrants treating latitude as continuous or as ordinal.