# How to make representative sample in dataset with two variables?

I have two variables and 1000 cases. How can I statistically find representative cases from total of 1000, based on statistical properties of both variables and correlation between them. Perhaps something based on T-test and 95% (or 99%) interval but for both variables? I would like to know which statistical method can find cases that have both values (simultaneously) statistically the most significant. I know that this deals with sample distribution and estimating the proportions.

• T-tests, significance, sample distributions, and estimates of proportions deal with conclusions you draw from the data. Finding "representative cases" is a matter of selecting cases from the dataset. The two activities are completely different. What, then, do you really want to do? – whuber Mar 10 '11 at 15:30
• Thank you for your answer. Indeed, I would like to find such cases that both data measurements (two variables) are in 99% (or 95 or 66) interval of their individual distributions. So it could be something like intersection (Boolean logic) of very significant data of two variables. Correlation between variables is 0.35275, one variable is we can say dependent on other but there are exceptions. – user3656 Mar 11 '11 at 10:16
• You just answered your own question: compute the interval endpoints and make the selection. But your references to "significant" and the implication that this procedure is "representative" are disconcerting because they suggest you are looking for an automatic or mindless way to discard the most interesting--and perhaps the most important--cases in your dataset; namely, those that don't lie in both intervals. The wisdom of that approach depends on what use will be made of the selection, which you haven't revealed. – whuber Mar 11 '11 at 15:30
• Aim of my whole procedure is: I will use selection for some further procedures in measurements. So at the beginning i have 1000 cases and six variables, after factor analysis, deleting some cases with one variable value and outlier test i get 53 cases and two variables. So i would like to know 99 95 or 66% confidence interval for variable 1 and 2 and select 5 to 10 cases for further work. – user3656 Mar 11 '11 at 21:49