Sampling

Sampling is the process of selecting a sample from a population of objects or individuals. The sample can be then examined to make conclusions about the entire population.

There are many different sampling methods, such as convenience sampling, self-selected sampling, systematic sampling, and random sampling. For example, suppose that a sample of the students in a classroom needs to be chosen to study blood sugar levels. The following applet visualizes some of these methods.

Since it may be impractical, too expensive, or even impossible to examine every member of a population, sampling is often used in real-world scenarios. Consider the following examples.

• Baseball cards are divided by teams. Then, five cards from each team are randomly selected to estimate the average RBI for the players.
• Every tenth person entering a music club is asked to name their favorite music genre.
• A website article on the tax increase invites readers to express their opinions on the government's decisions.
• A new drug is tested by a pharmaceutical company. Volunteers are divided randomly into two groups, one of which will receive the new drug, the second of which will receive a placebo.

Each sampling method influences the quality of the results of a statistical study. To make accurate and useful conclusions about a population, it is important to select an unbiased sample that is representative of the population that is examined.