CHAPTER PREVIEW

You already know that planning your study is the most difficult and time-consuming phase of the research process. You must come up with a question about a phenomenon you are interested in, and then devise a method for investigating the question. As part of the planning process, you must also consider how you are collecting information. You must be able to quantify what you are doing and what will happen in the study in a way that provides quantifiable characteristics. In addition to quantifying what you are doing within the study, it is important that you describe the participants in your study.

Researchers describe who participated and what happened in the study by using statistics. A statistic provides a quantitative measure for a sample or a subset of a population. A parameter is very similar to a statistic except that a parameter refers to some value in the population. We usually use statistics to describe results from our studies because we conduct research with samples of people.

We can quantify information by using one of two types of statistics, descriptive or inferential measures. Inferential statistics depend on probabilities, and we use them to test hypotheses. Descriptive statistics allow us to summarize information so that readers can quickly understand the outcomes of our study. In this chapter we will discuss how descriptive statistics are derived and how you might use them in your research.

Using Statistics to Describe Results

Popular media frequently report interesting statistics about a host of events or perceptions. For example, we often read reports about the percentages of people who belong to a political party or the average number of auto accidents that occur annually. Statistics, such as those published in the media, are usually presented as a way of describing interesting facts and figures. When we describe demographic characteristics, behaviors, or outcomes of a study, we are using a particular type of statistic called descriptive statistics.

The earliest known use of descriptive statistics occurred in 1662 when John Graunt published Observations on Bills of Mortalities in London, England. In this work, he summarized and reported information about the people who died from the plague (Stigler, 1986). Although these descriptive statistics relay information about a morbid topic, demographic information about the people who died from the plague is important for understanding the epidemiology of the disease.