research designs for quantitative studies ppt
TRANSCRIPT
RESEARCH
DESIGNS FOR
QUANTITATIVE
STUDIES
Dr. Jayesh Patidarwww.drjayeshpatidar.blogspot.com
What is a research design?
A researcher’s overall plan for obtaining answers to the research questions or for testing the research hypotheses is referred to as the research design.
Aspects of research design
Intervention
Comparison
Controls of extraneous variables
Timing of data collection
Research sites and settings
Communication with the study participants
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The following questions would be addressed
What exactly is the intervention?
What are the procedures to be used for
both groups?
Who will receive the intervention and who
will not? How will each group be selected?
What is the dosage of the intervention?
INTERVENTION
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INTERVENTION – Cont…
How long will the intervention be administered? And when will it begin?
Who will administer the intervention?
Will those administering the intervention are fully informed about the study? Will study participants be fully informed?
Under what conditions will the intervention be withdrawn or altered?
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COMPARISONS
In a quantitative study, the researcher specifies the nature of the comparisons in advance, where as in a qualitative study, comparisons may suggest themselves during the course of data collection.
TYPES OF COMPARISONS IN RESEARCH STUDIES
Comparison between two or more groups
Comparison of a single group at two or more points in time
Comparison of a single group under different circumferences or experience
Comparison based on relative rankings
Comparison with samples from other studies
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CONTROLS FOR EXTRANEOUS VARIABLES
The researcher must make decisions
about which extraneous variables to
control.
TIMING OF DATA COLLECTION
RESEARCH SITES & SETTINGS
COMMUNICATION WITH THE STUDY
PARTICIPANTS
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Overview of Research Design Types
Structured versus flexible designs Eg. Quantitative study and qualitative study
Between –subjects and within –subjects designs Eg. Testing the efficacy of a drug
1. One group administered
one group do not administered Between subjects design
2. Same group before, after
treatment Within subjects design
The time dimension
There are four situations in which it might be appropriate to
design a study with multiple points of data collection.
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1. Studying time related processes - Eg. Healing, earning, growth etc
2. Determining time sequences - Eg. Infertility results
in depression
3. Developing comparisons - Eg. Smoking and
lung
4. Enhancing research control - Eg. Two groups withalternative
interventions
Categorization of studies
• Cross sectional design
• Longitudinal design
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Longitudinal design
Types– Trend studies
– Cohort studies
– Cross-sequential design (Control studies with a
cross –sectional approach)
– Panel studies
– Follow-up studies
Retrospective versus prospective
designs
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Characteristics of good design
Appropriateness to the research question
Lack of bias
Precision
Power
Tips on designing research
Make a written list of the pros and cons of each
Balance a number of considerations, such as time, cost, ethical issues and the integrity of the study.
Anticipate alternative findings and consider whether design adjustments might affect the results.
Seek the advice of research experts in deciding the design
Write out a rationale for your choices one you have made your design decisions.
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Experimental Research designs for quantitative studies
Characteristics of true experiments
Manipulation – Involves doing something to at least
one group of subjects
Control – Refers to a group of subjects without
any manipulation
Randomization – involves the Placement of subjects
in groups on a random basis
Research designs
Experimental designs
Quasi experimental designs
Non experimental designs
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Types of experimental designs
Basic experimental design
Solomon four group design
Factorial design
Repeated measures design
Randomized clinical trials
Basic experimental design
Types
After only design or post test –only design (R-X-O)
Before after design or pretest –posttest design (R-O1 X O2)
(R-O1 – O2)
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Solomon four group design
Group Date collection
Before After
Experimental –with
pretest
X X
Experimental –
without pretest
- X
Control-with pretest X X
Control-without
pretest
- X
This design prevents, the post test measures
getting affected not only by the treatment but
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Factorial design
Types of stimulation Auditing tactile
A1 A2
A1 B1 A2 B1
A1 B2 A2 B2
A1 B3 A2 B3
15min B1 This design permits the testing
of multiple hypotheses in a
single experimental
Daily exposures
45m
B3
30min B2
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Repeated measures design
Randomized clinical trials
Advantages and disadvantages of experimental studies.
Advantage – Confidence with which causal
relationships can be inferred
– Most powerful method available to scientists
Disadvantage – Hawthorne effect limitation
– Number of like characteristics of human
beings, finance etc
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QUASI, EXPERIMENTAL RESEARCH
Quasi-Experimental designs
Non equivalent control group designs
Types
1.Non equivalent control group pre-test post –test design
(Quasi experimental)O1 X O2
O1 - O2
2. Non equivalent control group post test only design (Pre experimental)
X O
O
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Time series designs
Types
1. Time series design (Quasi –experimental)
O1 O2 O3 O4 X O5 O6 O7 O8
2. Time series non-equivalent control group design (quasi-
experimental)
O1 O2 O3 O4 X O5 O6 O7 O8
O1 O2 O3 O4 - O5 O6 O7 O8
3. Time series with intensified treatment (quasi-experimental)
O1 O2 X O3 O4 X+1 O5 O6 X+2 O7 O8
4. Time series with withdrawn and reinstituted treatment
(quasi-experimental)
O1 O2 X O3 O4 (–X) O5 O6 X O7 O8
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Advantages and disadvantages of the
quasi-experimental research
Advantages Feasibility
Generalizability some
extent
Practicality
Disadvantage Absent of control
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Non Experimental Research
Reasons for under taking non-experimental
research in nursing o Human characteristics are inherently not subject
to experimental manipulation (eg. blood typepersonality etc) and the effects of thesecharacteristics on some phenomenon of interestcannot be studied experimentally.
o For ethical reasons.
o Not practical to conduct a true experiment
o Experimental design is not appropriate to some
research questions
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Types of Non Experimental
Research
Ex post facto or correlational research
Descriptive research
1. Ex post facto design on correlational
research
Schematic diagram
Ex post facto design
Group A O
Group B O
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Descriptive research
Purpose
- To observe, describe and document
aspects of situation as it naturally
occurs
- To serve as a starting point of for
hypothesis generation or theory
development.
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Types
• Descriptive correlational study – No
control over the independent
variables
• Univariate descriptive studies – Not
focused on only one variable but to
describe the existing factors in terms
of frequency of occurrence
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Advantages:
An efficient and effective means of collecting a large amount of data about a problem area
Short time only
No biophysiologic or other measures are needed
Has an intrinsic appeal for the solution of many practical problems.
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Disadvantages:
Weak in its ability to reveal causal relationships
Susceptible to the possibility of faulty interpretation
Preexisting differences may be a plausible alternative explanation for any observed differences on the dependent variable of interest.
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SURVEY RESEARCH
EVALUATION RESEARCH
NEEDS ASSESSMENT
OUT COMES RESEARCH
SECONDARY ANALYSIS
META –ANALYSIS
DELPHI SURVEYS
METHODOLOGIC RESEARCH
METHODOLOGIC RESEARCH
CONTENT ANALYSIS STUDIES
ADDITIONAL TYPES OF
QUANTITATIVE RESEARCH
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