The latter does not produce representative samples. The first type of random sampling is called simple random sampling. It's the most basic type of random sampling. You will see below that, simple random samples are not the only equal probability sampling methods. It is the most basic and well know, however.
Researchers typically use a computer program that randomly selects their samples.
Then the program gives you a list of randomly selected numbers. Then you identify the people with those randomly selected numbers and try to get them to participate in your research study. Researchers often use a table of random numbers such as the one shown on page 161 of the book. Once you get the set of randomly selected numbers, find out who those people are and try to get them to participate in your research study. Systematic Sampling Systematic sampling is the second type of random sampling.