Descriptive Statistics

What Are Descriptive Statistics?

Descriptive statistics are used to tell people about the collected data in a study. They provide more information about the study’s samples and how they were measured.

Samples are the people or items that are selected from a population being studied. The results of the sampling are used to draw generalized conclusions about the larger group. Selecting individuals at random from a population provides a broad understanding of that population. For example, a researcher might select random people with various shades of hair for a study and then apply the results to everyone who lives there.

Narrowing the focus of a study to a smaller selected group and then taking samples from it provides more details about specific parts of the population. In this case, a researcher could select only redheaded people as his population and then select random redheads from the group. The results would provide a good idea of what redheads are like in a country but would tell little about the general population.

Statisticians call the overall population ‘N’ and the sample group ‘n.’ The sample group can be selected through a process much like drawing a prize-winning ticket out of a hat. This is known as “objective” sampling. On the other hand, statisticians may rely on a table of random numbers or use computer software that picks out people at random. This is known as “procedure” sampling.

The answers that people in the sample provide are called “responses.” Depending on what the researcher wants to find out about these people, they may be asked several questions requiring a response. A response is given a numerical value that can be recorded and measured. Using our redheads as an example, they could be asked if they are right- or left-handed, if they have blue or hazel eyes, or if they use sunscreen all of the time.
The researcher always gets the same answer when redheads are asked about their hair color: red. In this example, having red hair is what is known as a “constant.”

Different redheads will give different answers to the other questions. Hand dominance, eye color, and sunscreen use vary among redheads. These responses are called “variables.” By comparing these responses to redheadedness, the researcher can draw some conclusions about the people in the group.

For example, the researcher may find that left-handed redheads are more likely to use sunscreen and that hazel-eyed sample members tend to be left-handed. Therefore, left-handed redheads with hazel eyes will probably use sunscreen. Right-handed redheads with blue eyes will probably not use it. These two groups are the “norm.” Anyone who does not fall into either group “deviates” from the norm.

Arranged on a bell curve, the people in the normal group are clustered around the center of the graph. The deviants are represented by the thinner ends of the bell.

Researchers can determine more about the redheaded people in the sample by using other measurements and calculations that are too complex for a basic introduction to descriptive statistics.