For a given integer value k, D(3k+1)<D(3k+2), and D(3k+2)>D(3k+3), k=1,…,9999.

If I want to sample a subset of these 30000 data points for estimating the probability model for these data set, how should I choose the sample size or how to setup the sampling plan?

If I change the pattern to D(3k+1)<D(3k+2)<D(3k+3), how to determine the sampling plan?

Is there a formal methodology that I can follow for this kind of problem? Thanks a lot.