Mortality in Sample

Defining Mortality in an Investigation

Suppose a researcher wants to examine the effectiveness of a particular approach to the reduction of public speaking anxiety over time.[Page 1033] The investigation can be described as using a pretest survey, then three different 50-minute sessions involving material to reduce public speaking anxiety delivered once a week, and finally a posttest survey given a month after the ending of the sessions. Basically, the entire research process involves five separate contacts with the participants (pretest, session 1, session 2, session 3, and posttest).

At any point in the process, a participant may decide to drop out of the research investigation or due to circumstances become unable to complete the research investigation. Basically, if a person fails to participate in the pretest session, there exists no basis to make a comparison and therefore the rest of the four sessions become irrelevant. What this means is that the pretest becomes the largest sample and each subsequent session could become smaller as persons fail to participate in a particular session. The number of persons only becomes smaller with each passing session as the person is unable to participate. The application of the term mortality reflects the implication that each session, as persons drop out, become dead to the purposes of the investigation.

A central consideration of mortality in empirical investigation examines the reasons for noncompletion. The question of why a person was not completing each stage could be the result of some element of the investigation that relates to the process or outcome under consideration. If mortality becomes an issue due to size, the requirement of the investigator evaluating the reasons for the mortality becomes important. The reasons that a person does not complete the investigation require a follow-up and assessment to determine whether the process of outcome are impacted.

Implications and Evaluation of Mortality

The reasons for the person no longer continuing become the basis for the assessment of the impact of mortality. One of the first steps becomes an examination of whatever characteristics might differentiate the dropouts from those completing the investigation. If data collected examines such demographics as age, biological gender, education, socioeconomic status, race, religion, or nationality, then a comparison becomes possible. If no difference exists between those completing the investigation and those dropping out, then at least part of the argument for the equivalency of the groups becomes sustainable. The goal of these statistical evaluations involves the assumption that those persons continuing in the investigation did not differ from those dropping out.

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