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Quantitative Research Designs: Experimental, Quasi-Experimental, and Descriptive NOT for SALE OR DISTRIBUTION NOT for SALE OR DISTRIBUTION © Chad Baker/Getty Images © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE6 OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORQuantitative SALE OR DISTRIBUTION ResearchNOT FOR Designs: SALE OR DISTRIBUTION Experimental, Quasi-Experimental, © Jones & Bartlett andLearning, Descriptive LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER© Jones OUTLINE & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC ▶ IntroductionNOT FOR SALE OR DISTRIBUTION▶ Descriptive QuantitativeNOT Designs FOR SALE OR DISTRIBUTION ▶ Experimental Study Designs ▶ Additional Types of Designs ▶ Quasi-Experimental Designs ▶ Researcher Interview: Intervention Research, Dr. Leslie Cunningham-Sabo, PhD, RDN © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORLEARNING SALE OR DISTRIBUTION OUTCOMES NOT FOR SALE OR DISTRIBUTION ▶ Discuss five considerations when planning a ▶ Discuss the advantages and disadvantages of research design. various quasi-experimental designs. ▶ Explain the three essential components of ▶ Compare and contrast the descriptive cross- © Jones & Bartlett Learning,experimental LLC designs, and compare and© Jones & Bartlettsectional, Learning,repeated cross-sectional, LLC comparative, contrast the following experimental designs: and descriptive correlational designs. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION randomized controlled trials, crossover, factorial, ▶ Discuss the advantages and disadvantages of and Solomon four group designs. various descriptive designs. ▶ Discuss the advantages and disadvantages of ▶ Read a research study and identify the design various experimental designs. used and analyze study results. ▶ Compare© Jones and contrast & Bartlett the nonequivalent Learning, LLC ▶ Distinguish between© secondaryJones & data Bartlett analysis Learning, LLC controlNOT group FOR and interruptedSALE OR time DISTRIBUTION series and secondary research.NOT FOR SALE OR DISTRIBUTION designs. © JonesINTR & BartlettODU Learning,CTION LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Designing a research study requires making a number of decisions on the steps you will take to answer your research question(s). Like an architect, you need to prepare a blueprint for your project. If you have ever met with an architect before, you know that © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 155 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION 9781284126464_CH06_PASS02.indd 155 12/01/17 2:53 pm © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 156 Chapter 6: Quantitative Research Designs: Experimental, Quasi-Experimental, and Descriptive NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the process usually starts with a lot of questions. Research design is no different. The following questions address a number of key design features that must be considered. ©1. Jones What &is theBartlett research question?Learning, Will thereLLC be an intervention? Testing© the Jones effects of& anBartlett Learning, LLC NOT interventionFOR SALE is theOR hallmark DISTRIBUTION of experimental and quasi-experimentalNOT FOR research. SALE OR DISTRIBUTION If there is an intervention with human participants, the researcher will assign participants to be exposed to the independent variable, such as a modified diet or nutrient supplement, or be part of the control group. Experimental and quasi- experimental designs are used to test a hypothesis. © Jones & Bartlett2. Instead Learning, of an intervention, LLC will researchers observe ©study Jones participants & Bartlett and take Learning,measure- LLC NOT FOR SALE ORments? DISTRIBUTION For example, researchers might observeNOT a group FOR over SALE a longer OR periodDISTRIBUTION of time to see if exposure to certain factors (such as a diet high in fruits and vegetables) affects their risk of disease. This type of design is called a cohort study design. It is commonly used in the field of epidemiology, a discipline within public health that looks at the rates of health-related states (such as disease) in dif- © Jones & Bartlett Learning, LLCferent groups of people and why© Jones they occur, & Bartlett and then looks Learning, at how this LLC informa- NOT FOR SALE OR DISTRIBUTIONtion can be used to control healthNOT problems. FOR SALE Study ORdesigns DISTRIBUTION used in epidemiology are discussed in Chapter 7. 3. What are the variables? What comparisons are going to be made between or within groups? Comparisons are needed to examine relationships between the indepen- dent and the dependent variable. ©4. Jones When & and Bartlett how often Learning,will data be collected LLC or measurements taken? Many© Jonesexperimental & Bartlett Learning, LLC NOT studiesFOR measureSALE ORthe dependent DISTRIBUTION variable at least before and after theNOT intervention. FOR SALE OR DISTRIBUTION Weight loss studies, for example, often take measurements for a year or more to see whether participants kept the weight off. Data may be collected at just one point in time, such as in a cross-sectional study, or more frequently. In a longitudinal study, participants are observed and measurements are taken over © Jones & Bartletta longLearning, period of LLC time. Longitudinal studies either© Jones go forward & Bartlett in time (prospec Learning,- LLC NOT FOR SALE ORtive) DISTRIBUTION or backward in time (retrospective). NOT FOR SALE OR DISTRIBUTION 5. What will the setting be for the study? The setting could be a hospital, community center, or other location. Some studies use multiple sites. 6. In an intervention study with at least two groups, will the participants be randomly assigned to a group? True experimental research involves random assignment to groups © Jones & Bartlett Learning, LLCso participants each have an© equal Jones chance & Bartlett of receiving Learning, any of the LLC treatments NOT FOR SALE OR DISTRIBUTION(including no treatment) underNOT study. FOR Quasi-experimental SALE OR DISTRIBUTION research does not have randomization of participants to groups. 7. In a human intervention study, will participants, researchers, and staff be blinded from knowing to which group a participant was assigned? Blinding helps to prevent or minimize sources of bias, such as expectation bias. Expectation bias is when © Jonesresearchers’ & Bartlett expectations Learning, of what LLCthey believe the study results ©should Jones be get & inBartlett Learning, LLC NOT theFOR way SALE of accurately OR DISTRIBUTIONtaking measurements and reporting results.NOT FOR SALE OR DISTRIBUTION 8. What controls will be put in place to reduce the influence of extraneous variables? Extra- neous variables are factors outside of the variables being studied that might influence the outcome of a study and cause incorrect conclusions. A good quan- titative design identifies and rules out as many of these competing explanations © Jones & Bartlettas Learning, possible. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION A good research design helps you answer the research question while effectively reducing threats to design validity. Quantitative research designs are often used to look at causal relationships, but they can also be used to look at associations or relationship between variables. Quantitative © Jones & Bartlett Learning,research LLC studies can be placed into one© of Jones five categories, & Bartlett although Learning, some categories LLC do vary NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION 9781284126464_CH06_PASS02.indd 156 12/01/17 2:53 pm © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Experimental Study Designs 157 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION a bit from book to book. First are experimental designs with an intervention, control group, and randomization of participants into groups. Next are quasi-experimental designs with© Jones an intervention & Bartlett but no Learning, randomization. LLC Descriptive designs do not© Jones have & Bartlett Learning, LLC an intervention or treatment and are considered nonexperimental. They usually aim to provide informationNOT FOR about SALE relevant OR variables DISTRIBUTION but do not test hypotheses. Good descrip-NOT FOR SALE OR DISTRIBUTION tive studies provoke the “why” questions of analytic (cause-and-effect) research. Two additional categories are epidemiologic and predictive correlational designs. When you read about designs in this chapter, examples of studies are given to illus- © Jonestrate & the Bartlett design. The Learning, examples includeLLC some discussion of the© results Jones of statistical & Bartlett tests, Learning, LLC as well as sample tables from the studies. In a quantitative study, statistics are often used NOT FORto answer SALE one ofOR these DISTRIBUTION questions: NOT FOR SALE OR DISTRIBUTION 1. Is there a difference among the groups? Example: “LA Sprouts: A Garden-Based Nutrition Intervention Pilot Pro- gram Influences Motivation and Preferences for Fruits and Vegetables in Latino © Jones & Bartlett Learning,Youth” LLC ( Journal of the Academy of Nutrition© Jones
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