Dr.(Mrs.) A.V.Raman

Dean

Omayal Achi College of Nursing

Avadi, Chennai

EXPERIMENTAL DESIGN

INTRODUCTION TO RESEARCH DESIGNSINTRODUCTION TO RESEARCH DESIGNSQuantitative research designQuantitative research design

• Research design of a study spells out the basic strategies that researchers adopt to develop evidence that is accurate and interpretable

• The research design incorporates some of the most important methodological decisions that the researchers make particularly in quantitative studies

ASPECTS OF QUANTITATIVE ASPECTS OF QUANTITATIVE RESEARCHRESEARCH

• Intervention

• Comparisons

• Control of extraneous variables

• Timing of data collection

• Research sites and settings

• Communication with the subjects

INTERVENTION

In some studies nurse researchers want to test the effect of specific intervention on dependent variable (for e.g.. the effect of specific intervention on labor and neonatal outcome)

COMPARISON

The most common types of comparisons are

1. Comparisons between two or more groups (The hypothesis that the drug tamoxefin reduced the rate of breast cancer in high risk women could be tested by comparing women who received tamoxefin and those who did not)

2.In certain instances it is desirable to make comparisons for the same study participants

(e.g. studying patients heart rate before and after intervention,

Comparing low back pain for patients lying in two different positions)

CONTROLS FOR EXTRANEOUS VARIABLES

The complexity of relationships among human characteristics often makes it difficult to answer research questions unless efforts are made to isolate key research variables and control other factors extraneous to the research questions

TIMING FOR DATA COLLECTIONTIMING FOR DATA COLLECTION

In most studies data are collected from In most studies data are collected from subjects at a single point of time (for e.g. the subjects at a single point of time (for e.g. the subjects might be asked on a single subjects might be asked on a single occasion to describe the health promotion occasion to describe the health promotion behavior)behavior)

In some designs we contact the subjects In some designs we contact the subjects in multiple time (e.g. to observe the growth in multiple time (e.g. to observe the growth pattern 3 monthly) Hence the researcher pattern 3 monthly) Hence the researcher must decide on the number of data must decide on the number of data collection points needed to address the collection points needed to address the research question properlyresearch question properly

RESEARCH SITES AND SETTINGS sites are the overall location for

research Settings are the more specific place

where data collection will occur sites and settings to be selected so as to

maximize the validity and reliability of th data in designing a study. The setting should be natural and avoid anxiety promoting or foreign to the subjects experiences

COMMUNICATION WITH THE SUBJECTSCOMMUNICATION WITH THE SUBJECTS Decide how much information to be Decide how much information to be

given to the participantsgiven to the participants Full disclosure of the study?Full disclosure of the study? Consent Oral or written?Consent Oral or written? Think about the reading and Think about the reading and comprehension level of the subjectscomprehension level of the subjects Who will provide the information?Who will provide the information? What additional questions from the What additional questions from the

subjects subjects are expected?are expected? Debriefing sessions?Debriefing sessions?

EXPERIMENTAL EXPERIMENTAL DESIGNDESIGN

Science answers questions with experiments

EXPERIMENTAL DESIGNEXPERIMENTAL DESIGNAn experiment is a scientific An experiment is a scientific

investigation in which investigation in which observations are made and observations are made and data are collected according data are collected according to a set of well defined to a set of well defined criteria. In an experiment, criteria. In an experiment, researchers are active agents researchers are active agents not passive observers.not passive observers.

The procedures developed The procedures developed by physical scientists were by physical scientists were

profitably adopted by profitably adopted by biologists during the 19biologists during the 19thth

century, resulting in many century, resulting in many achievements in physiology achievements in physiology

and medicine.and medicine.

DEFINITIONDEFINITION Experimental method is an Experimental method is an empirical research method empirical research method

used to examine a used to examine a hypothesized causal hypothesized causal relationship between relationship between

independent and dependent independent and dependent variablesvariables. .

Begin by asking a question about your topic

One that is testable with the materials at hand

What is a good question for an experiment?

DEFINE THE PROBLEM

Now we need a hypothesis Now we need a hypothesis to guide our investigation.to guide our investigation.

What is a hypothesis?

Your best thinking about how the change you make might affect another factor. Tentative or trial solution to the question. An if ………… then ………… statement.

CHARACTERISTICS OFCHARACTERISTICS OF EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN

A true experimental design is characterized by Manipulation, Control , and randomization

Refers to the process by which the researcher manages the independent variable in order to study the effect on the dependent variable.

MANIPULATION

EXAMPLE. Gentle massage is effective as a pain relief

measure for elderly nursing home residents The Independent variable is gentle massage

which could be manipulated by giving some patients the massage intervention and withholding it for others

Then it is possible to compare the pain level (dependent variable) in the two group to see if differences in receipt of the intervention resulted in degree of pain levels

CONTROL

The experiment must be organized so that the extraneous factors are prevented from operating and confusing the outcome which is to be appraised.

Control is acquired by manipulating by randomizing, by careful preparation of the experimental protocols, and by the use of a comparison group or groups.

EXAMPLEEXAMPLE

• If a researcher wanted to supplement diet of the low birth baby with a particular nutrient for 2 weeks, the weight gain at the end of 2 weeks would tell us nothing about the treatment effectiveness

Suppose an average 1 kg. weight gain is noted does this gain support the conclusion that nutrition supplement (IV) caused the weight gain (DV)

The answer will be NO? because babies The answer will be NO? because babies normally gain weight as they maturenormally gain weight as they mature

Without a control group- a group that does not Without a control group- a group that does not receive the nutritional supplements it is receive the nutritional supplements it is impossible to separate the effects of impossible to separate the effects of maturation from those treatment maturation from those treatment

Therefore the term Therefore the term CONTROL GROUPCONTROL GROUP refers to a group of subjects whose refers to a group of subjects whose performance on a dependent variable is used performance on a dependent variable is used to evaluate the performance of the to evaluate the performance of the experimental group on the same dependent experimental group on the same dependent variablevariable

RANDOMISATIONThe term random essentially means that every

subject has an equal chance of being assigned to any group. Randomization is the process that first ensures every unit in the target population has an equal chance of being chosen for the study sample, and then ensures that each unit in the study sample has on equal chance of being assigned to either the experimental or the control group.

EXAMPLEEXAMPLE

The effectiveness of a contraceptive health education programme for multiparous women. Two groups of subjects were included .One group was given intervention and other was not. The women in the sample are likely to differ in age, education, and attitude This would affect the woman's diligence in practicing contraception

Although randomization is a preferred Although randomization is a preferred scientific method for equalizing the scientific method for equalizing the groups, there is no guarantee that the groups, there is no guarantee that the group will in fact be equal Therefore we group will in fact be equal Therefore we need a procedure to consciously control need a procedure to consciously control of those characteristics of subjects that of those characteristics of subjects that are likely to affect the outcome is called are likely to affect the outcome is called MATCHING (e.g. if matching were used in MATCHING (e.g. if matching were used in contraceptive education, then the contraceptive education, then the researcher might ensure that if there was researcher might ensure that if there was a married 38 year old woman with six a married 38 year old woman with six children in exp. Group, then there will also children in exp. Group, then there will also be 38 year old woman with six children in be 38 year old woman with six children in control groupcontrol group

The antecedent event in a proposed causal sequence is called the “independent variable”.

The measured effect in the causal sequence is called the “dependent variable”.

Eight classes of extraneous variables may especially interfere with research on human subjects, history, maturation, testing, instrumentation, statistical regression selection, mortality and interaction among these.

1.History, the specific events occurring between the first and second

measurement in addition to the experimental variables

2. Maturation2. Maturation,, process within the process within the respondents operating as a function of the respondents operating as a function of the passage of time per se (not specific to the passage of time per se (not specific to the particular events), including growing older, particular events), including growing older, growing hungrier, growing more tired and the growing hungrier, growing more tired and the likelike

3. Testing,3. Testing, the effects of taking a test upon the effects of taking a test upon the scores of a second testingthe scores of a second testing

4.4. InstrumentationInstrumentation,, in which changes in in which changes in the calibration of a measuring instrument or the calibration of a measuring instrument or changes in the observers or scores used may changes in the observers or scores used may produce changes in the obtained produce changes in the obtained measurementsmeasurements

5. Statistical regression, operating where groups have been selected on the basis of their extreme scores

6. Biaser resulting in differential selection of respondents for the comparison groups ?

7. Experimental mortality, or differential loss

of respondents for the comparison groups8. Selection-maturation interaction etc.,

which in certain of the multiple group quasi-experimental designs, might be mistaken for the effects of the experimental variable.

PRINCIPLE GUIDELINES OF EXPERIMENTS

The MAX-MIN-CON. By Kerlinger 1986.

The abbreviation stands for the following.

MAX-Maximize experimental variable

MIN- Minimize error variance.

CON-Control extraneous variance.

MAJOR STEPS IN MAJOR STEPS IN EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN

1.1. Delineate the population or universe to Delineate the population or universe to be studied (i.e. the set of subjects or be studied (i.e. the set of subjects or objects that share a common observable objects that share a common observable characteristic)characteristic)

2. Select a sample from the population by 2. Select a sample from the population by random sampling random sampling

3. By random assignment, sub-divide the 3. By random assignment, sub-divide the sample into two sub-samplessample into two sub-samples

4.. Specify one sub-sample, the 4.. Specify one sub-sample, the experimental group and other the control experimental group and other the control groupgroup

5. Before introducing the independent 5. Before introducing the independent variable, observe and record all variable, observe and record all important characteristics of the two important characteristics of the two groupsgroups

6.6. Introduce the independent variable into Introduce the independent variable into the experimental group but withholds it the experimental group but withholds it from the control groupfrom the control group

7. After introducing the independent 7. After introducing the independent variable, observe the dependent variable variable, observe the dependent variable in both experimental and control groupin both experimental and control group

8. Compare the changes that occur in 8. Compare the changes that occur in the experimental group with those the experimental group with those that may have occurred in the that may have occurred in the control groupcontrol group

9.9. Record the difference Record the difference 10.Compare these values with 10.Compare these values with

statistically computed values that statistically computed values that judge the significance of the judge the significance of the difference, and indicate whether or difference, and indicate whether or not the observed differences could not the observed differences could have occurred by chance. have occurred by chance.

TYPES OF EXPERIMENTAL DESIGN

The investigator planning an experiment has many experimental design option to choose. Experimental designs fall into three major categories.

a)True or classical experimental design

b)Quasi-experimental design

c)Pre-experimental design.

TRUE OR CLASSICAL EXPERIMENTAL DESIGN

• TRUE OR CLASSICAL EXPERIMENTAL DESIGN

• True or classical experimental design includes six major designs. They are

• Pre-test___ post - test control group design

• Solomon four – group design • After/ post - test __ only

experimental design • Factorial design• Randomized block design• Cross over design or repeated

measures design.

The most commonly used in nursing studies, are discussed as nomenclature used and

definitions developed by Campbell and Stanley ( 1963).

The standard notations that are helpful in under standing alternative experimental design are -

‘x’ To denote the experimental manipulation. (Treatment or intervention)

‘O’ To denote observations or measurement

‘R’ To denote randomization

1.PRE-TEST POST-TEST CONTROL GROUP DESIGN

Pretest Experimental Treatment

Control group

Post

test

Experimental

groupRandom assignme

ntPretest Post test

EXAMPLEEXAMPLE

Effectiveness of antenatal nutrition education on pregnancy and labor outcome among primi para mothers attending out patient department of selected hospitals Madurai 2007-2009

2. Solomon four group design is a complex particularly useful in studies of developmental phenomena and permits the investigator to differentiate many effects.

Pretest Experimental Treatment

Control group

Experimental

group

Control group

Post testExperimental

group

Random assignment

Pretest Post test

Experimental Treatment

Post test

Post test

EXAMPLEEXAMPLE

Effectiveness of workshop on management of HIV to improve the nurses attitude toward patients with AIDS admitted in selected hospitals , Madurai 2006-2008

3. Post- test only control groups design this design, which is sometimes called after only control group designs, is composed of two randomly assigned groups, but neither of which is pre tested or pre measured in the before period of time.

Control group

Post

-test

Post

-test Experimental

group

Experimental

treatment

Random assignment

EXAMPLEEXAMPLE Effects of holding the newborns on Effects of holding the newborns on

paternal bonding behavior paternal bonding behavior The researcher randomly assigned The researcher randomly assigned

36 first time fathers attending 36 first time fathers attending uncomplicated deliveries of normal uncomplicated deliveries of normal infants to experimental and control infants to experimental and control group (Those who held and did not group (Those who held and did not hold their infants at delivery)12-36 hold their infants at delivery)12-36 hours after the babies were born hours after the babies were born bonding behavior frequencies were bonding behavior frequencies were recorded and observed the outcomerecorded and observed the outcome

4. 4. Factorial designFactorial design

In this design testing of multiple In this design testing of multiple hypotheses is done in a single experimenthypotheses is done in a single experiment

In factorial experiments subjects are assigned In factorial experiments subjects are assigned at random a specific combination of at random a specific combination of conditions conditions

e.g. Does auditory stimulations have a more e.g. Does auditory stimulations have a more beneficial effect on the development of beneficial effect on the development of premature infants than tactile stimulation?premature infants than tactile stimulation?

(effect is weight gain and cardiac (effect is weight gain and cardiac responsiveness)responsiveness)

EXAMPLEEXAMPLE

AUDITORY

A1

TACTILE

A2

15 Min

B1

A1 B1 A2 B1

30 Min.

B2

A1 B2 A2 B2

45 Min.

B3

A1 B3 A2 B3

Type of stimulation

Daily

Exposure

5. Randomized Block Design There are two factors (independent

variables) but one factor is not experimentally manipulated.

e.g. Compare the effects of tactile versus auditory stimulation for female vs male infants.

It can be structured as 2x2 experiment, with type of stimulation as one factor and gender as the other factor

6. Cross over design (or Repeated measures design)

It involves the exposure of the same subjects to more than one experimental treatment

e.g. Effectiveness of two alternative back rest position ( flat, horizontal vs. 30o elevation) on intracranial and cerebral perfusion pressures in brain injured adults

PRE-EXPERIMENTAL DESIGNS

1. The one –shot case study or single case study

→ The study design has a total absence of control, it is considered to be little value as an experiment.

2.One-GroupPretest-posttest design

Only one group is observed before and after the independent variable is introduced. Loss of the control group decreases the usefulness of the study but may be necessary in cases where it is not possible or feasible to have control groups

EXAMPLEEXAMPLE

Effectiveness of selected Effectiveness of selected nursing intervention on nursing intervention on knowledge and level of knowledge and level of satisfaction among clients satisfaction among clients with strokewith stroke

ADVANTAGES OF EXPERIMENTAL ADVANTAGES OF EXPERIMENTAL DESIGNDESIGN

1.True experiments are the most powerful 1.True experiments are the most powerful method for testing hypothesis of cause and method for testing hypothesis of cause and effect relationship between variable because of effect relationship between variable because of the rigours, precision and control properties of the rigours, precision and control properties of experimental design.experimental design.

2. 2. This ‘if then’ type of relationship is important This ‘if then’ type of relationship is important to nursing and medical researchers because of to nursing and medical researchers because of its implications for predication and its implications for predication and explanation.explanation.

3.Though the control imposed by manipulation comparison and randomization, alternative explanation to a cause interpretation can be ruled out or discredited.

DISADVANTAGES OF DISADVANTAGES OF EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN

1.1. Some variables are not feasible or Some variables are not feasible or ethical to manipulate e.g., assessing ethical to manipulate e.g., assessing pregnant women to take a new drug pregnant women to take a new drug found to be dangerous to fetal found to be dangerous to fetal development would not be ethically development would not be ethically possible.possible.

2.2. Randomization and otherwise equal Randomization and otherwise equal treatment of control and experimental treatment of control and experimental group can occur in a laboratory, but group can occur in a laboratory, but these conditions do not resemble what these conditions do not resemble what goes under real world conditions, and goes under real world conditions, and experimental findings can therefore be experimental findings can therefore be based on rather artificial circumstancebased on rather artificial circumstance

3. 3. Experimental design attempt to Experimental design attempt to reduce variable to measurable reduce variable to measurable terms. Many of the phenomena terms. Many of the phenomena that are important to science in that are important to science in nursing are complex, nursing are complex, multidimensional and holistic, and multidimensional and holistic, and defy the reductionism that has defy the reductionism that has worked reasonably in the physical worked reasonably in the physical or natural sciences.or natural sciences.

QUASI EXPERIMENTAL DESIGN

DEFINITIONDEFINITION

It is a research design in It is a research design in which the researcher initiates which the researcher initiates an experimental treatment but an experimental treatment but some characteristics of a true some characteristics of a true experiment is lacking.experiment is lacking.

PURPOSESTo provide alternative means of

examining causality in situations not conducive to experimental group.

To facilitate the search for knowledge and examination of causality in situations in which complete control is not possible.

RANDOM ASSIGNMENTRANDOM ASSIGNMENT

It is a procedure used to It is a procedure used to assign subjects to assign subjects to treatment or control treatment or control groups randomly.groups randomly.

COMPARISON GROUPS

Comparison groups are not selected using random sampling and do not receive the experimental treatment.

Types of comparisons groups:Groups that receive no treatment.Groups that receive placebo treatmentGroups that receive usual treatment.Groups that receive second experimental

treatment.

TYPES OF QUASI EXPERIMENTAL DESIGN.

QUASIEXPERIMENTAL

DESIGN

Interrupted times series

design

Non equivalent control group

design

NON EQUIVALENT NON EQUIVALENT COMPARISON COMPARISON

GROUP DESIGNSGROUP DESIGNS

1. ONE GROUP POSTTEST ONLY 1. ONE GROUP POSTTEST ONLY DESIGNDESIGN

It is referred to as pre-experimental rather than quasi experimental where manipulation of Independent variable is done and posttest is conducted to measure the outcome.

Manipulation of

Dependent variable

Treatment

Measurement of

Independent variable Post test

Example

Outcome of Antenatal Education on pregnancy and labor .

2. POSTTEST ONLY DESIGN WITH A 2. POSTTEST ONLY DESIGN WITH A COMPARISON GROUPCOMPARISON GROUP

In this design a comparison group is In this design a comparison group is introduced to determine the efficacy of the introduced to determine the efficacy of the treatment and after manipulation of treatment and after manipulation of independent variable only posttest is independent variable only posttest is conducted.conducted.

Treatment

Experimental Group

Post test

Treatment

Non equivalent control group

Post test

Introducing Computer education to improve staff morale

3. One Group Pretest-Posttest Design

In this design the experimental group is expected to serve as a comparison group. Pretest and posttest scores are used to find the efficiency of the treatment.

Experimental Group

Pre-test Treatment Post test

•Effectiveness pelvic floor muscles exercises in control of incontinence of urine.

•Effectiveness of infection control policy to decrease infection in postnatal ward.

4. PRE-TEST & POSTTEST DESIGNS WITH 4. PRE-TEST & POSTTEST DESIGNS WITH A COMPARISON GROUPA COMPARISON GROUP

In this design the comparison group In this design the comparison group is not randomly selected. The is not randomly selected. The analysis is made on examining the analysis is made on examining the differences between comparison differences between comparison group and experimental group group and experimental group pretest, between pretest and post pretest, between pretest and post test, between comparison group and test, between comparison group and experimental group posttest.experimental group posttest.

Experimental group

Pre- test Treatment Post-test

Non equivalent control group

Pre-test Post-test

Example:

Effectiveness of education on partograph in assessing labour progress among nurses working in labour rooms

INTURRUPTED TIME SERIES INTURRUPTED TIME SERIES DESIGNDESIGN

It is similar to descriptive time series design It is similar to descriptive time series design except that a treatment is applied at s given except that a treatment is applied at s given point in time and the outcome is measured point in time and the outcome is measured at different point of time In at different point of time In simple simple interrupted time series design there is interrupted time series design there is no control or comparisonno control or comparison group group

Use of multiple methods to measure the Use of multiple methods to measure the outcome greatly strengthenoutcome greatly strengthen the design.the design.

Experimental groupExperimental group

Pre-testPre-test T T Post testPost test

O(1)O(2) O(3)O(1)O(2) O(3) o(1) o(2) o(3) o(1) o(2) o(3)

EXAMPLE

Effectiveness of selected nutritional interventions on growth and development pattern of children attending under fives clinic at Omayal Achi community health centre at Tiruvalluvar district 2006- 2008

Interrupted Time series designs with Interrupted Time series designs with a comparison group a comparison group

Comparison group allows examination of Comparison group allows examination of differences in trends between groups after the differences in trends between groups after the treatment and of the persistence of treatment treatment and of the persistence of treatment effects overtimeeffects overtime

Experimental groupExperimental groupPre-testPre-test T T Post testPost test o(1) o(2) o(3) o(1) o(2) o(3)o(1) o(2) o(3) o(1) o(2) o(3)Comparison groupComparison groupPre-testPre-test TT Post test Post testo(1)o(2) o(3)o(1)o(2) o(3) o(1) o(2) o(3) o(1) o(2) o(3)

ADVANTAGES & DISADVANTAGES OF ADVANTAGES & DISADVANTAGES OF QUASI EXPERIMENTAL STUDIESQUASI EXPERIMENTAL STUDIES

Advantages:Advantages:From the point of view of controls for From the point of view of controls for

internal validity quasi experimental internal validity quasi experimental designs are thought to be superior to pre designs are thought to be superior to pre experimental design.experimental design.

Disadvantages:Disadvantages:Cannot test causal hypothesis Cannot test causal hypothesis Do little to ensure external generalizability. Do little to ensure external generalizability.