The Structure of Quantitative Studies

Abstract

This chapter introduces the methods of quantitative studies. It describes the process of measurement, which is fundamental to all quantitative methods, and then offers an important distinction between measurement and demonstration studies. The chapter concludes with a description of three types of demonstration studies: descriptive, interventional, and correlational.

Answers to Self-tests

Self-test 6.1

• 1. The attribute is “appropriateness” of each alert. “Alerts” comprise the object class. (Although the panelists need access to the cases to perform the ratings, cases are not the object class here because each alert is what is directly rated—the attribute of “appropriateness” is a characteristic of each alert—and because each case may have generated multiple alerts related to its different clinical aspects.) The instrumentation is the rating form as completed by a human judge. Each individual judge’s rating of the appropriateness of an alert constitutes an independent observation.

• 2. The attribute is “knowledge about the administrative information system.” Staff members are the object class. The instrument is the written test. Each question on the test constitutes an independent observation.

• 3. The attribute is “ease of use” of the app. Tasks are the object class. The independent observations are the ratings by each tester.

Self-test 6.2

• 1. Ratio

• 2. Ordinal

• 3. Ratio

• 4. Ordinal

• 5. Nominal

• 6. Nominal

• 7. Interval (In IQ testing, the average score of 100 is completely arbitrary)

Self-test 6.3

This is a measurement study. The stated purposes of the study have nothing to do with the actual quality of TraumAID’s advice. The purposes are exclusively concerned with how well this quality, whatever it turns out to be, can be measured. The quality of TraumAID’s advice would be the focus of a separate demonstration study.

Self-test 6.4

• 1. It is an interventional study because the study team presumably had some control over where the resource was or was not deployed. The site is the “subject” for this study. (Note that this point is a bit ambiguous. Patients could possibly be seen as the subjects in the study; however, as the question is phrased, the enrollment rates at the sites are going to be the basis of comparison. Because the enrollment rate must be computed for a site, then site must be the “subject.”) It follows that the dependent variable is the protocol enrollment rate; the independent variable is the presence or absence of the resource.

• 2. It is a descriptive study. Nurses using the system are the subjects. There is no independent variable. Dependent variables are the extent of workstation use for each purpose.

• 3. It is a correlational study. Patients are the subjects. The independent variables are the characteristics of the patients; the dependent variable is the extent of use of information resources.

• 4. This is also a correlational study. Patients are the subjects. The independent variable is the genetic information; the dependent variable is the diseases they develop. There is, however, no manipulation or purposeful intervention.

• 5. Interventional study. Students are the subjects. Independent variable(s) are the version of the database and time of assessment. The dependent variable is the score on each problem-solving assessment.