research designs for quantitative studies. what is a research design? a researcher’s overall plan...

RESEARCH DESIGNS FOR QUANTITATIVE STUDIES

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

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

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Under what conditions will the intervention be withdrawn or altered?

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

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

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 todesign a study with multiple points of data collection.

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

with alternative

interventions Categorization of studies • Cross sectional design • Longitudinal design

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

Characteristics of good designAppropriateness 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.

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 designsQuasi experimental designs Non experimental designs

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)

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 also by exposure to the pre-test

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

45mB3

30min B2

Repeated measures designRandomized 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

QUASI, EXPERIMENTAL RESEARCH

Quasi-Experimental designs Non equivalent control group designsTypes 1.Non equivalent control group pre-test post –test

design (Quasi experimental)

O1 X O2O1 - O2

2. Non equivalent control group post test only design (Pre experimental)

X OO

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

Advantages and disadvantages of the quasi-experimental research

Advantages Feasibility

Generalizability some

extent

Practicality

Disadvantage Absent of control

Non Experimental Research

Reasons for under taking non-experimental research in nursing

o Human characteristics are inherently not subject to experimental manipulation (eg. blood type personality etc) and the effects of these characteristics on some phenomenon of interest cannot be studied experimentally.

o For ethical reasons.o Not practical to conduct a true experimento Experimental design is not appropriate to some

research questions

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

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.

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

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.

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.

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