Bad ways to sample 1 – Opportunity sampling

Opportunity sampling - Simply selecting those that are available at the time. 

This is one of the most common types of statistical sampling using students as subjects for the research because the opportunity to use them is so easy for universities.

Son, these are your opportunities.

Dad, I’m choosing this one because it’s the nearest.

This is the weakest and most unreliable form of sample selection. Data are collected from individuals who are conveniently available.

Opportunity sampling could include going up to people in class and asking them to be interviewed.

Problems with opportunity sampling

Opportunity sampling can result in a biased survey due to the opportunity of the people available. For example, if you were in your maths class and wanted to conduct a survey of pupils at the school to judge what they thought of lessons, then asking people in the maths class would be an example of opportunity sampling. This would create a bias, however, towards the opinion of maths students and may not be reflective of other groups of students such as those studying PE or drama, or those who studied maths under a different tutor.

Example 1

List the advantages and disadvantages of opportunity sampling.

Answer:

Example 2

A restaurant used opportunity sampling when it asked the 2 customers it had at 4pm on Tuesday afternoon what the service was like.  Why may this be an unreliable sampling method?

Answer:

The restaurant is unlikely to have many customers at 4pm on Tuesday and so the staff will not be very busy or rushed having to attend to other customers, allowing them to devote more time to the two surveyed, which could result in the restaurant receiving better responses than if they surveyed customers at a busier time such as 7:30pm.