A free app for Android, by N. G. Tech.

This app is intended to be a reference and a guide for students, new researchers, and experienced researchers. It simulates a flowchart that will assist you in choosing an appropriate sampling technique for research purposes. If you are new to research, or want to learn more about sampling, the app provides valuable information.

If you want to make inferences from the data, you will need to choose a method of sampling. There are various methods, and the choice will depend on your study and research objectives. 

The app recommends using a probability sampling technique if your study requires you to make inferences from the data. If the data can be collected from the entire population or a sample must be taken, the app will recommend a non-probability sampling technique. The app also recommends using a particular technique if your study requires face-to-face contact with respondents, the geographical area over which the population is spread, and other characteristics of the population.