Home >> Science & Nature >> Science

Definition of Sample Size in Research Project Steps

Though rarely possible, the most accurate way to study a research question --- particularly relating to humans and human behavior --- is to study an entire population. Instead, scientists must rely on samples. The results of a research project based on a sample are then generalized to fit the entire population. One of the most vital steps in choosing a sample for a project is identifying and selecting a sample size.

Purpose of Sampling
- Sampling is a process used in research to obtain data points in a research study. This process is completed in multiple ways. For example, simple random sampling consists of selecting participants from the population completely at random. Stratified sampling involves choosing participants at random based on certain categories, including gender and race, to obtain a sample representative of the entire population.
Sample Size
- The sample size chosen for any given research project usually depends on the level of accuracy that you will accept from the results of the project. Statistically speaking, most fields of study accept results with a margin of error plus or minus .05 as credible, meaning there is a 5 percent chance that the results obtained were due to error. Statisticians calculate the sample size needed to obtain this level of accuracy based on several factors relevant to the particular study, such as desired margin of error and critical standard score.
Accuracy and Credibility
- As a general rule in research, the larger the sample size for any given project is, the better. Larger samples represent the actual data of a population more accurately than smaller samples. This observation has roots in the idea of the normal distribution curve. A larger sample size takes into account more data and thus eliminates outliers and other unusual data that smaller sample sizes may highlight. The ideal minimum sample size to lend credibility to a research project varies based on field but typically ranges from 40 to 100 participants.
Inadequate Sample Size
- Inadequate sample size in a research project casts doubts upon the results of the project. A too-small sample size may admit outliers and other unusual data points into the results of the study, causing the sample data to vary from the actual population data. This causes the results of a research study to lack representation and prevents you from generalizing the data from the study to the larger population; in short, a too-small sample size renders the results of a study useless.

Science