Convenience sampling

Convenience sampling (also known as grab sampling, accidental sampling, or opportunity sampling) is a type of non-probability sampling that involves the sample being drawn from that part of the population that is close to hand. This type of sampling is most useful for pilot testing. Convenience sampling is not often recommended for research due to the possibility of sampling error and lack of representation of the population. But it can be handy depending on the situation. In some situations, convenience sampling is the only possible option. For example, a college student who is doing a term project and wants to know the average consumption of soda in that college town on Friday night will most probably call some of his friends and ask them how many cans of soda they drink, or go to a nearby party to do an easy survey. There is always a trade-off between this method of quick sampling and accuracy. Collected samples may not represent the population of interest and therefore be a source of bias. In the example above, if said college town has a small population and mostly consists of students, and that particular student chooses a graduation party for survey, then his sample has a fair chance to represent the population. Larger sample size will reduce the chance of sampling error occurring. Another example would be a gaming company that wants to know how one of its games is doing in the market one day after its release. Its analyst may choose to create an online survey on Facebook to rate that game. The major challenge of this approach will be reaching to the people who play games. As social media is a vast place, it's always difficult to collect samples from the population of interest. Most people may not be interested or take the survey seriously while completing it, which results in sampling error. The survey may be improved greatly if the analyst posts it to fan pages dedicated to game lovers. He may find a lot more people in that group who would be inclined to judge and rate the game critically.