1 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Chapter 8 Clarifying Quantitative Research Designs

2 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Research Design  Blueprint or detailed plan for conducting a study  Purpose, review of literature, and framework provide the basis for the design

3 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Study Purpose  To describe variables  To examine relationships  To determine differences  To test a treatment  To provide a base of evidence for practice  A combination of above

4 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Design Characteristics  Maximizes control over factors to increase validity of the findings  Guides the researcher in planning and implementing a study  Not specific to a particular study, but linked to other steps of the research process

5 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Concepts Relevant to Design  Causality  Multicausality  Probability  Bias  Control  Manipulation

6 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Causality  There is a cause-and-effect relationship between the variables.  The simplest view is one independent variable causing a change in one dependent variable.  Independent variable (X) causes Y (a change in the dependent variable).

7 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Multicausality  There is a cause-and-effect relationship between interrelating variables.  There are multiple independent variables causing a change in the dependent variable.

8 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Causality:AB Pressure Ulcer Multicausality: Years smoking High-fat diet Heart disease Limited exercise Diagram of Causality and Multicausality

9 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Probability  The likelihood of accurately predicting an event  Variations in variables occur.  Is there relative causality?  Therefore, what is the likelihood that a specific cause will result in a specific effect?

10 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Bias  The slanting of findings away from the truth  Bias distorts the findings.  Research designs should be developed to reduce the likelihood of bias or to control for it.

11 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Potential Causes of Bias in Designs  Researchers  Components of the environment and/or setting  Individual subjects and/or sample  How groups were formed  Measurement tools  Data collection process  Data and duration of study (maturation)  Statistical tests and analysis interpretation

12 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Control  Implemented throughout the design  Improved accuracy of findings  Increased control in quasi-experimental research  Greatest in experimental research

13 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Manipulation  Implementation of a treatment or intervention  The independent variable is controlled.  Must be careful to avoid introduction of bias into the study  Usually done only in quasi-experimental and experimental designs

14 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Elements of a Strong Design  Controlling environment: selection of study setting  Controlling equivalence of subjects and groups  Controlling treatment (Tx)  Controlling measurement  Controlling extraneous variables

15 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing a Study Design  Was the type of design identified?  Was the study design linked to the purpose and/or objectives, questions, or hypotheses?  Were all variables manipulated or measured?

16 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing a Study Design (cont’d)  If the study included a treatment, was it clearly described and consistently implemented?  Were extraneous variables identified and controlled?  What were threats to design validity in study?

17 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing a Study Design (cont’d)  Was a pilot study performed?  What was reason for pilot and the outcome?  Study feasibility  Refine design or treatment  Examine validity and reliability of measurement methods

18 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing a Study Design (cont’d)  How adequate was the manipulation?  What elements should have been manipulated to improve the validity of the findings?  Based on your assessment of the adequacy of the design, how valid are the findings?  Is there another reasonable (valid) explanation (rival hypothesis) for the study findings other than that proposed by the researcher?

19 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing a Study Design (cont’d)  Identify elements controlled in the study.  Identify possible sources of bias.  Are there elements that could have been controlled to improve the study design?  What elements of the design were manipulated and how were they manipulated?

20 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Types of Quantitative Research Designs  Descriptive study designs  Correlational study designs  Quasi-experimental study designs  Experimental study designs

21 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Diagramming the Design  Clarifies variables to be measured or manipulated  Indicates focus of study: description, relationships, differences, and/or testing a treatment  Identifies data collection process: time for study, treatment implementation, measurement of variables  Provides direction to data analysis

22 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Descriptive Study Designs  Typical descriptive design  Comparative descriptive design  Case study design

23 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Typical Descriptive Design  Most commonly used design  Examines characteristics of a single sample  Identifies phenomenon, variables, conceptual and operational definitions, and describes definitions

24 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Comparative Descriptive Design  Examines differences in variables in two or more groups that occur naturally in a setting  Results obtained from these analyses are frequently not generalizable to a population

25 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Case Study Design  Exploration of single unit of study (i.e., family, group, or community)  Even though sample is small, number of variables studied is large.  Design can be source of descriptive information to support or invalidate theories.  It has potential to reveal important findings that can generate new hypotheses for testing.  There is no control.

26 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Correlational Design  Descriptive correlational design  Predictive correlational design  Model testing design

27 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Determining Type of Correlational Design

28 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Descriptive Correlational Design  Describes variables and relationships between variables  There is no attempt to control or manipulate the situation.

29 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Predictive Correlational Design  Predicts value of one variable based on values obtained for other variables  Independent and dependent variables are defined.  Independent variables most effective in prediction are highly correlated with dependent variables  Required development of theory-based mathematical hypothesis proposing variables expected to effectively predict dependent variable

30 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Model Testing Design  Tests accuracy of hypothesized causal model (middle-range theory)  All variables are relevant to the model being measured.  A large, heterogeneous sample is required.  All paths expressing relationships between concepts are identified.

31 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Advantages of Experimental Designs  More controls: design and conduct of study  Increased internal validity: decreased threats to design validity  Fewer rival hypotheses

32 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Essential Elements of Experiments 1. Random assignment of subjects to groups 2. Researcher-controlled manipulation of independent variable 3. Researcher control of experimental situation and setting, including control/comparison group 4. Control of variance Clearly spelled out sampling criteria Precisely defined independent variable Carefully measured dependent variable

33 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Quasi-experimental Design  Untreated control group design with pretest and posttest  Nonequivalent dependent variables design  Removed-treatment design with pretest and posttest

34 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Advantages of Quasi-experimental Design  More practical: ease of implementation  More feasible: resources, subjects, time, setting  More readily generalized: comparable to practice

35 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Study Groups  Groups in comparative descriptive studies  Control group  Comparison group  Equivalent vs. nonequivalent groups

36 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Randomized Clinical Trial  The design uses large number of subjects to test a treatment’s effect and compare results with a control group who did not receive the treatment.  The subjects come from a reference population.  Randomization of subjects is essential.  Usually multiple geographic locations are used.

37 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Experimental Interventions  Interventions should result in differences in posttest measures between the treatment and control or comparison groups.  Intervention could be physiological, psychosocial, educational, or a combination.  Nursing is developing a classification system for interventions.

38 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing Guidelines for Interventions  Was the experimental intervention described in detail?  Was justification from the literature provided for development of the intervention, and what is the current knowledge?  Was a protocol developed to ensure consistent implementation of the treatment?  Did the study report who implemented the treatment?

39 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Critiquing Guidelines for Interventions (cont’d)  Was any control group intervention described?  Was an intervention theory provided to explain conclusions?

40 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Mapping the Design  O = Observation or measurement  T = Treatment

41 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Two-Group Experimental Design PretestTreatmentPosttest Experimental groupO1O1 TO2O2 Control or comparison group O1O1 O2O2

42 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Quasi-experiment with Several Posttests Posttests PretestTreatment1 Mo 2 Mo 3 Mo 4 Mo Experimental groupO1O1 TO2O2 O3O3 O4O4 O5O5 Control or comparison group O1O1 O2O2 O3O3 O4O4 O5O5

43 Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Replication Research  Replication or repeating a study to confirm original findings  Establishes credibility for the findings  Provides support for theory development  Encouraged for novice or new researchers  First clinical research project