5 External validity: Sampling

So far, you have learnt to ask a RQ, identify different ways of obtaining data, and design the study.

In this chapter, you will learn how to obtain the sample to study. You will learn to:

• distinguish, and explain, precision and accuracy.
• distinguish between random and non-random sampling.
• select random samples.
• identify, describe why random samples are preferred over non-random samples.
• identify, describe and use simple random sampling.
• identify, describe and use systematic sampling.
• identify, describe and use stratified sampling.
• identify, describe and use cluster sampling.
• identify, describe and use multistage sampling.
• identify ways of obtaining samples that are more likely to be representative samples.