Question

A group of researchers is interested in studying the income of Canadian university graduates one year after graduation. They decide to take a sample of 3,000 recent university graduates for their study. Indicate whether each of the following scenarios describes a probability or non-probability sample and indicate the type of sampling procedures used if it is a probability sample. Make sure to explain your answer.

1. The researchers obtain a full list of graduates from each Canadian university, assign each individual an ID number, and then take a random sample of 3,000 individuals with the help of a random number generator.

2. The researchers obtain a full list of graduates from each university and assign each individual an ID number. However, because they are interested in how outcomes vary by GPA, they divide the graduates into three groups with GPAs of 0.1-2.0, 2.1-3.0, and 3.1-4.0. They then select random samples from each of these groups.

3. The researchers decide to create an online survey to target Canadians who recently graduated from university. They advertise this survey on Facebook. After receiving 3,000 responses from recent university graduates, they close the survey and analyze their data.

4. Instead of obtaining a full list of graduates from each university in Canada, the researchers select six universities at random. They obtain lists of graduates from these six universities, collect samples of 500 recently graduated students from each university, and then use these individuals for their study.

Answer 1

Probability sampling is based on the fact that every member of a population has a known and equal chance of being selected in the population. while non-probability sampling relies on the subjective judgement of the researcher.

1. Probability sampling.

Because all graduates in Canadian universities have equal chance of being selected in sample.

2. Probability sampling.

This is a stratified sampling.

3. Non probability sampling

Because they didn't consider all population. They consider only the graduates who uses facebook. Each unit in population does not have equal chance of being selected in sample.

4. Probability Sampling.

This is a stratified sampling.