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Research involves a controlled, systematic approach to obtain an answer to a question.1 A number of research types are recognized:


  • Experimental research: involves the manipulation of a variable and then measuring the effects of this manipulation.1 A variable is a measurement of phenomena that can assume more than one value or more than one category (see later).1
  • Nonexperimental research: does not manipulate the environment but may describe the relationship between different variables, obtain information about opinions or policies, or describe current practice.1
  • Basic research: generally thought of as laboratory-based research in which the researcher has control over nearly all aspects of the environment and subjects.1
  • Clinical or applied research: refers to research that seeks to solve practical problems by finding solutions to everyday problems, cure illness, and develop innovative technologies.


Statistics is a branch of applied mathematics concerned with finding patterns in data and inferring connections between events.2 A number of statistical terms and definitions are outlined in Table 3-1.

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Table 3-1. Statistical Terms and Definitions 
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Study Pearl

Much of the initial groundwork in statistics concerns making an accurate guess, or hypothesis.


Populations and Samples


A population consists of all subjects (human or otherwise) that are being studied.


  • Prevalence: the proportion of a population who has a particular disorder or condition at a specific point in time.
  • Incidence: a rate of development of new cases of a disorder in a particular at-risk population over a given period of time.
  • Parameter: a characteristic or measure obtained by using all the data values from a specific population.


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