Experimental Research Design

Jasleen Kaur Brar

INTRODUCTION

Research design is the framework or guide used for the planning, implementation, and analysis of a study.

It is a systematic plan of what is to be done, how it will be done, and how the data will be analysed.

Experimentation is the most scientifically sophisticated research method.

It is observation under controlled conditions. In experimental design researcher is an active

agent rather than passive observer.

DEFINITION

Research design: It can be defined as a blue print of research study, which enables the researcher to know on whom, what, when, where, and how the study will be conducted.

Experimental research design: Experimental research designs are concerned with examination of the effect of independent variable on the dependent variable, where the independent variable is manipulated through treatment or intervention(s), and the effect of these interventions is observed on the dependent variable.Or

According to Riley, experimental research design is a powerful design for testing hypotheses of causal relationship among variables.

ELEMENTS OF RESEARCH DESIGN

Qualitative Research design includes the five major elements. These are:

Elements of research design

Tools & method(s) of data collection

Time and place of data collection

The approach

Method of data analysisPopulation, sample and sampling technique

Qualitative

Quantitative

Or both

With/without conceptual framework

SELECTION OF RESEARCH DESIGN

Research designs are plans and the procedures for research. To meet the aims and objectives of a study, researchers must select the most appropriate design.

Factors affecting selection of research design

Nature and purpose of the research problem

Researcher's knowledge and experience, interest and motivation

Research ethics and principles

Subjects/participants

Resources and time

TYPES OF RESEARCH DESIGN

Research designs are classified into two broad categories and several subtypes.

Quantitative research designs Qualitative research designs

A. QUANTITATIVE RESEARCH DESIGNSTypes of research design Broad categories

1. Experimental research design True experimental designPost-test-only control designPre-test-posttest control group designSolomon four-group designFactorial design Randomized block designCrossover design

Quasi experimental design Nonrandomized control group design Time-series design

Pre-experimental design One-shot case design One-group pretest-post-test design

TYPES OF RESEARCH DESIGN

1. Non-experimental research designs a. Descriptive design Univarent descriptive design Exploratory descriptive design Comparative descriptive design

b. Correlational/ex post facto design Prospective design Retrospective design

c. Developmental research design Cross-sectional design Longitudinal design

d. Epidemiological designs Case-control studies Cohort studies

e. Survey research designA. QUALITATIVE RESEARCH DESIGN a. Phenomenological research

b. Ethnographic research c. Grounded theoryd. Case studiese. Historical researche. Action research

TRUE EXPERIMENTAL DESIGNS

The true research design are those where researchers have complete control over the extraneous variables and can predict confidently that the observed effect on the dependent variable is only due to the manipulation of the independent variable.

Main characteristics

Manipulation: it refers to conscious control of the independent variable by the researcher through treatment or intervention(s) to observe its effect on dependent variable.

Control: it refers to the use of control group and controlling the effects of extraneous variable in which researcher is interested.

Randomization: it means that every subject has and equal chance of being assigned to experimental or control group. Randomization is used in true experimental research designs to minimize the threat of internal validity of the study and to eliminate the effect of extraneous variables on dependent variable.

Types of True Experimental Designs

Post test only Pretest post-test only Soloman 4 groups Factorial design Randomized block design Cross over design

Post test only control design: composed of two randomly assigned groups, i.e.

experimental and control but neither of which is pretested before the administration of treatment on the experimental group.

For example, to study the effect of an educational intervention related to urinary incontinence on the subsequent help seeking behaviour of older adults. Experimental

group Treatment Post-test

Control group Post-test

Random assignment

Pretest post-test only: subjects are randomly assigned to either the experimental or control group.

The effect of the dependent variable on both the groups is seen before the treatment.

Later the treatment is carried out on experimental group only, and after treatment observation of dependent variable is made on both the groups to examine the effect of the manipulation of independent variable on the dependent variable.

For example, such a design can be used for ‘an experimental study to assess the effectiveness of cognitive behavioural therapy interventions for patients with breast cancer.’

Experimental group Pretest Treatment Post-test

Control group Pretest Post-test

Random assignment

Soloman 4 group design: there are two experimental groups (experimental group 1 and experimental group 2) and two control groups (control group 1 and control group 2).

The investigator randomly assigns subjects to four groups. Out of the four groups, only experimental group 1 and control group 1 receives the pretest, followed by the treatment to the experimental group 1 and experimental group 2.

Finally, all the four groups receive post-test, where the effects of the dependent variables of the study are observed and comparison is made of the four groups to assess the effect of independent variable on dependent variable.

The soloman four group design is believed to be the most prestigious experimental research design because it minimizes the threat to internal and external validity.

Exp group 1 Treatment Post-test

Control group 1 Post-test

Exp group 2 Treatment Post-test

Control group 2 Post-test

Random assignment

Pretest

Pretest

Factorial design: the researcher manipulates two or more independent variables simultaneously to observe their effects on the dependent variables.

This design is useful when there are more than two independent variables, called factors to be tested.

For example, a researcher wants to observe the effects of two different protocols of mouth care prevention of VAP when performed at different frequencies in a day.

Frequency of mouth care

Protocols of mouth care

Chlorohexidine(α1) Saline (α2)

4 hourly(β1) (α1) ..(β1) (α2) ..(β1)

6 hourly(β2) (α1) ..(β2) (α2) ..(β2)

8 hourly(β3) (α1) ..(β3) (α2) ..(β3)

This design also facilitates the testing of several hypothesis at a single time. Typical factorial design incorporates 2x2 or 2x3 factorial, but it can be any combination. The first number (α) refers to the independent variables or the types of experimental treatments, and the second number (β) refers to the level or frequency of the treatment.

Randomized block design: when there are large number of experimental comparison groups, the randomized block design is used to bring homogeneity among selected different groups.

This design looks similar to factorial design in structure, but out of two factors, one factor is not experimentally manipulated.

For example, a researcher wants to examine the effects of three different types of antihypertensive drugs on patients with hypertension. To ensure the homogeneity among the subjects under treatment, researcher randomly places the subjects in homogeneous groups (blocks).

Types of antihypertensive drugs

Blocks Pts. With primary hypertension (I)

Diabetic pts. With hypertension (II)

Renal pts. With hypertension (III)

A A, I A, II A, IIIB B, I B, II B, IIIC C, I C, II C, III

There are two factors: type of antihypertensive drugs and type of patients with hypertension, where only the type of drug is manipulated and types of patients with hypertension are simply grouped in different blocks with similar characteristics to ensure homogeneity.

Cross over design: in this design, subjects are exposed to more than one treatment, where subjects are randomly assigned to different orders of treatment. It is also known as ‘repeat measures design’.

For example, when we are comparing the effectiveness of chlorohexidine and saline mouth care protocol, first we administer the chlorohexidine mouth care protocol on group 1 and saline mouth care protocol on subjects of group 2.

Groups PROTOCOLS OF MOUTH CARE

Group I chlorohexidine(α1) saline(α2)

Group I saline(α2) chlorohexidine(α1)

Later the treatment is swapped where group 1 receives saline mouth care and group 2 receives chlorohexidine. In such studies, subjects serve their own control.

Advantages Considered most powerful

designs

Greater degree of purity

Conditions not found in natural setting can be created in experimental setting

Conditions can be created in short period of time that may take years to occur naturally

Disadvantages Ethical problems

Many of human variables neither have valid measurable criteria nor instruments to measure them.

Not possible to impose control over extraneous variables in natural settings

Difficult to get cooperation from study subjects