Examples of Sampling Survey

In many situations, there are people who need to make a survey design using sampling techniques. In this case, someone wants to make a survey, with a small sampling size and a large level of accuracy to obtain better information with very few error intervals.

Well, if this is your case you will find useful to use the computer program POSDEM. This is a computer program that optimizes the selection in survey design. You could use a free version to test it. It is not a 100% full operative version, yet, but it allows you to made survey designs as if you were an expert in sampling methods.

To simplify the first aproximation to POSDEM, we have prepared two examples with diferente degrees of difficulty. The first one for "beginners" in surveys design, and the second one for "advanced" users.

Examples for beginners

Suposse that you have been working recently for a big statistic departament, and that someone mistook you for your boss, and took charge to make a sampling design. He gave you a data base with the list of suppliers of a company and he request you maximun precision for the smallest sampling size and, he said, "we don´t want to contamine our suppliers". With these specifications, you, that didn't notice of the mistake, remain seriously concerned.

The first thing you could make is look for an other employment. Nevertheless, if you find the courage to continue in this job, you could observe the data you have to make the investigation. You realize the different lists and see that the firm has 400 suppliers, and that each one has his capital and his level of purchases of the last year.

With this specifications in mind:

- to study few suppliers, with the maximun precission. Wath could this mean?

- the population frame is 400 suppliers from last year. Auxiliar variables: capital and level of purchases.

you access to the Internet, search for "Surveys design", and find the POSDEM address. You download a free version of POSDEM and the example for beginners. Now, I have my technical report, and I have the units that made my sample, also the units that didn't response and all this with a totally professional aspect. Examples for beginners

Now, when you show your work to your boss, who understands the possibilities of the program, he gets curious, obtains his own free copy and goes to the example for advanced users.

Examples for advanced users

With the same data from the past example, the boss, who understands the superpopulation approach, makes the appropiate analysis and he obtains a detailed report. It allows him to select the best method for this population structure. Examples for advanced users