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Experimental research design


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Experimental research design

  2. 2. INTRODUCTION… Experimental is most scientificallysophisticated research method. It is defined as ‘observation under controlledconditions’. Experimental research design are concernedwith examination of the effect of independentvariable on the dependent variable, where theindependent variable is manipulated throughtreatment or intervention(s), & the effect ofthose interventions is observed on thedependant
  3. 3.
  4. 4. CONCEPT…True experimental research designsare those where researchers havecomplete control over the extraneousvariables & can predict confidentlythat the observed effect on thedependable variable is only due to themanipulation of the
  5. 5. ESSENTIAL CHARACTERISTICS… A true experimental research design must essentiallyconsist of the following three characteristics: Manipulation Control
  6. 6. MANIPULATION: Manipulation refers to conscious control ofthe independent variable by theresearcher through treatment orintervention(s) to observe its effect on thedependent variable. In other words, it is a conscious act by theresearcher, where he or she varies theindependent variable & observes theeffect that manipulation has on thedependant variable of
  7. 7. COUNT… For example, a researcher is conducting astudy on efficacy of cholrhexidine mouthwashon the prevention of ventilator-associatedpneumonia (VAP) among patients admitted inICUs. In this example, chlorhexidine mouthwash isthe dependent variable, which is manipulatedby the researcher, & is used as anintervention for the experimental group, whilethe control group is kept deprived of it toobserve its effect on the incidence of
  8. 8. CONTROL: Control is another essential element of trueexperimental design. Control refers to use of control group &controlling the effects of extraneousvariables on the dependent variable inwhich researcher is interested. The subject in the control & experimentalgroups are similar in number &characteristics, but the subject in the controlgroup receive no experimental treatment orany intervention at
  9. 9. COUNT… The experimental group receives the plannedtreatment or intervention & a comparison ismade with the control group to observe theeffect of this treatment or intervention. Generally in health care & nursing research, itis not ethically feasible keep a control groupdeprived of interventions; however, existingconventional method of interventions may becompared with experimental
  10. 10. RANDOMIZATION: Randomization means that every subject has an equalchance of being assigned to experimental or of studysubjects on a random basis. Through random assignment of subject underexperimental or control group, chances of systemic biasis eliminated. Randomization is used in true experimental researchdesign to minimize the threat of internal validity of thestudy & to eliminate the effect of extraneous variables ondependent variables. Through randomization, on average the characteristics ofthe subject in experimental & control groups are similar,thus influence of extraneous variables on dependantvariable is eliminated by dispersing the variability of thesubject characteristics equally in both the
  11. 11. COUNT…METHODS OF RANDOMIZATION: Random assignment of subject may done with simple flipof a coin for each subject; if coin lands on its ‘head’,subjects are assigned to first group & with ‘tail’ subjectsare assigned to control group. Another possible method is to write the names of thesubjects on slips of paper & put the slips into a bowl &then draw lots. The first designated numbers of subjectsare placed in one group, & rest are assigned underanother group. Thirdly a random table may be used to facilitate therandomization process. In this method, blind-foldedsubjects choose a number from a table of numberhorizontally (row) or vertically (columns), till a requisitenumber is reached for both experimental & controlgroups. Computer-assisted random sequences also maybe used for the random assignment of the
  12. 12. TYPES OF THRUE EXPERIEMNTAL DESIGNwww.drjayeshpatidar.blogspot.comTrue Experiential DesignPost-testonlyFactorialPretestpost-testonlyCrossoverSolomon 4groupsRandomizedblock
  13. 13. POST-TEST-ONLY CONTROL DESIGN: Composed of two randomly assigned group, i.e.experimental & control, but neither of which is pretestedbefore the implementation of treatment on theexperimental group. In addition, while treatment is implement on theexperimental group only, post-test observation is carriedout on both the group to assess the effect ofmanipulation. This design can be helpful in situations where it is notpossible to pretest the subjects. For example, to study the effect of an educationalintervention related to urinary incontinence on thesubsequent help-seeking behavior of older
  14. 14. COUNT…www.drjayeshpatidar.blogspot.comRandomassignmentExp. group Treatment Post-testControl group Post-test
  15. 15. PRETEST-POST-TEST-ONLY DESIGN In this research designs, subjects are randomly assignedto either the experimental pr the control group. The effect of the dependent variable on both the groupsis seen before the treatment (pretest). Later, the treatment is carried out on experimental grouponly, & after-treatment observation of dependant variableis made on both the groups to examine the effect of themanipulation of independent variable on dependantvariable. For example, such a design could be used for ‘anexperimental study to assess the effectiveness ofcognitive behavioral therapy interventions for patientswith breast cancer.’
  16. 16. COUNT…www.drjayeshpatidar.blogspot.comRandomassignmentExp.groupTreatmentPost-testControlgroupPost-testpretestpretest
  17. 17. SOLOMON FOUR-GROUP DESIGN There are two experimental groups (experimental group1 & experimental group 2) & two control groups (controlgroup 1 & control group 2). Initially, the investigator randomly assigns subjects to thefour groups. Out of the four groups, only experimental group 1 &control group1 receives the pretest, followed by thetreatment to the experimental group 1 & experimentalgroup 2. Finally, all the four groups receive post-test, where theeffects of the dependant variables of the study areobserved & comparison is made of the four groups toassess the effect of independent variable (experimentaltreatment) on the dependant
  18. 18. COUNT… In this, experimental group 2 was observed atone occasion, & that score should be similar toaverage scores of those in experimental &control groups. To estimate the amount of change inexperimental & control group 2, the averagetest scores of experimental & control groups 1are used as baseline The solomon four-group design is believed tobe most prestigious experimental researchdesign, because it minimizes the threat tointernal & external
  19. 19. COUNT…www.drjayeshpatidar.blogspot.comRandomassignmentExp. Group 1Control Group 1Exp. Group 2Control Group 2pretest treatment Post-testpretest Post-testtreatment Post-testPost-test
  20. 20. FACTORIAL DESIGN In factorial design, researcher manipulates two or moreindependent variables simultaneously to observe their effects onthe dependant variables. This design is useful when there are more than two independentvariables, called factors to be tested. For example, a researcher wants to observe the effect of twodifferent protocols of mouth care on prevention of VAP whenperformed at different frequencies in a day. This design also facilitates the testing of several hypothesis at asingle time. Typical factorial design incorporates 2X2 or 2X3 factorial, but itcan be in any combination. The first number (α) refers to the independent variables or thetype of experimental treatments, & the second number (β) refersto the level or frequency of the
  21. 21. COUNT…Frequencyof mouthcareProtocols of the mouth careChlorhexidine(α1)Saline (α2)4 hourly (β1) α1….β1 α2….β16 hourly (β2) α1….β2 α2….β28 hourly (β3) α1….β3 α2….β
  22. 22. RANDOMIZED BLOCK DESIGN Control of inherent differences betweenexperimental subjects & differences inexperimental conditions is one of the difficultproblems faced by researcher in biologicalsciences. When there are a large number of experimentalcomparison groups, the randomized blockdesign is used to bring homogeneity amongselected different groups. This is simple method to reduce the variabilityamong the treatment groups by a morehomogeneous combination of the subjectsthrough randomized block
  23. 23. COUNT… For example, a researcher wants to examinethe effects of three different antihypertensivedrugs on patients with hypertension. In this example, to ensure the homogeneityamong the subjects undertreatment, researcher randomly places thesubjects in homogeneous groups (blocks) likepatients with primary hypertension, diabeticpatients with hypertension, & renal patientswith hypertension
  24. 24. COUNT…Types ofantihypertensivedrugsBlocksPatients withprimaryhypertension (I)Diabetic patientswith hypertension (II)Renal patientswithhypertension(III)A A, I A, II A, IIIB B, I B, II B, IIIC C, I C, II C,
  25. 25. CROSSOVER DESIGN In this design, subjects are exposed to more than onetreatment, where subjects are randomly assigned todifferent orders of treatment. It is also known as ‘repeat measures design’. This design is more efficient in establishing the highestpossible similarity among subjects exposed to differentconditions, where groups compared obviously haveequal distribution of characteristics. Through crossover design is considered as an extremelypowerful research design, sometimes it is not effectivebecause when subjects are exposed to two differentconditions, their responses of the second condition maybe influenced by their experience in the first
  26. 26. COUNT… For example, when we are comparing theeffectiveness of the chlorhexidine mouth care protocolon group I & saline mouth care protocol on the subjectsof group II. Later, the treatment is swapped, where group Ireceives the saline mouth care & group II receiveschlorhexidine. In such studies, subjects serve as theirown control.www.drjayeshpatidar.blogspot.comGroups Protocols of the mouth careGroup I Chlorhexidine (α1) Saline (α2)Group II Saline (α2) Chlorhexidine (α1)
  27. 27. ADVANTAGES OF TRUE EXPERIMENTALDESIGN Experimental research designs are considered themost powerful designs to establish the causalrelationship between independent & dependantvariables. Where the purpose of research is explanation,causal relationship may be established among thevariables by experimentation, especially in studiesinvolving physical objects, where the variables aremore easily controlled than in human studies. In this studies, the controlled environment in whichthe study is conducted can yield a greater degreeof purity in
  28. 28. COUNT… Conditions not found in a natural setting can be created inan experimental setting, where the independent variable ismanipulated by investigator. In the experimental approach, we can often createconditions in a short period of time that may take years tooccur naturally. For example, in genetic studies we canbreed strains in very small time, which would take a longtime in nature to occur. When the experiment is conducted in a laboratory,experimental unit, or other specialized research setting, itis removed from the pressure & problems of real-lifesituations & the researcher can pursue his or her studies ina more leisurely, careful, & concentrated
  29. 29. DISADVANTAGES OF TRUE EXPERIMENTAL DESIGN Most of the times, the results of experimental researchdesigns cannot be replicated in studies conducted onhuman beings due to ethical problems. For certain research problems, because of the danger tophysical & psychological health of the human subjects, itis not possible to conduct experiments on human beings. Many of the human variables neither have validmeasurable criteria nor instruments to measure them. Forexample, patient welfare or level of wellness cannot bemeasured on any scale or by any instrument. In thesesituations, if a refined experimental design is used, theremay be a mismatch of research design & the variable-measuring
  30. 30. COUNT… In experimental studies conducted in naturalsettings like hospitals or community, it is notpossible to impose control over extraneousvariables. Another disadvantage of the experimentalresearch design is that it is very difficult to getcooperation from the study participants,because it may involve medical or surgicaltreatment or intervention, which may make theprospective subjects reluctant to participate inresearch
  31. 31. QUASI –
  32. 32. INTRODUCTION… Quasi-experimental research design involves themanipulation of independent variable to observe to effecton dependant variable, but it lacks at least one of the twocharacteristics of the true experimental design;randomization or a control group. In other words, quasi-experimental designs have anelement of manipulation but lack at least one of the othertwo properties that characterize true experiments;randomization or a control group. Quasi-experimental designs are generally used toestablish the causality (effect of independent variable ondependent variable) in situations where researchers arenot able to randomly assign the subjects to groups or forvarious reasons no control group is available for anexperimental
  33. 33. MAIN CHARACTERISTICS… Manipulation of the independent variables toobserve the effects on the dependant variables. Lack of at least one of the two other essentialcharacteristics of the true experiment, i.e.random assignment of subject or a controlgroup. Quasi-independent variables are used insteadof true independent variables. Whereindependent variable is not manipulates incomplete controller
  34. 34. TYPES OF QUASI-EXPERIMENTAL DESIGNNonrandomized control group designTime-series
  35. 35. NONRANDOMIZED CONTROL GROUP DESIGN It is also known as the ‘nonequivalent control groupdesign’. This design is identical to the pretest-posttest controlgroup design, except there is no random assignment ofsubjects in experimental & control groups. In this design, experimental & control groups are selectedwithout randomization, & dependent variables areobserved in experimental as well as control groupsbefore the intervention. Later, the experimental group receives treatment & afterthat posttest observation of dependant variables iscarried out for both the groups to assess the effect oftreatment on experiment
  36. 36. COUNT...www.drjayeshpatidar.blogspot.comExp. groupControl groupPretestPretestTreatment Post-testPost-test
  37. 37. COUNT… For example, this method was used to study ‘the effects ofintegrated care on quality of work in nursing homes: a quasi-experiment’. The purpose of this study was to examine the implementation ofintegrated care in the nursing home sector, & its effect on the qualityof work of the caregivers. A nonequivalent pretest-posttest control group design was used inthis study. Data was collected by through a questionnaire. The result showed that the intervention appeared to be onesuccessful on the somatic wards. The caregivers of these wards were more successful in creating ahome-like environment for their residents. Regarding the effects of the intervention on the quality of workfactors, the result included an increase of social support bysupervision. The intervention on the psychosomatic wards was unsuccessful,through the introduction of integrated care on the somatic wardswas fairly
  38. 38. TIME-SERIES DESIGN This design is useful when the experimenter wants tomeasure the effects of a treatment over a long period of time. The experimenter would continue to administer the treatment& measure the effects a number of times during the course ofthe experiment. Generally it is a single-subject research, in which theresearcher carries out an experiment on an individual or on asmall number of individuals, by alternating betweenadministering & then withdrawing the treatment to determinethe effectiveness of the O1 O3O2 O3O2O1Treatment
  39. 39. COUNT… A researcher might assess pain levels of agroup of patients with low-back pain. After 3weeks of pain assessment, subjects aretaught special exercises to reduce that pain.During the next 3 weeks, pain levels wouldagain be measured. Measuring a child’s school performance ona weekly basis, & then introducing a newteaching technique. Then again measuringon a weekly
  40. 40. ADVANTAGES OF QUASI-EXPERIMENTAL DESIGN Quasi-experimental designs are more frequently usedbecause they are more practical & feasible to conductresearch studies in nursing, where in the absence of alarge sample size, randomization &/ or availability ofcontrol groups are not always possible. This design is more suitable for real-world natural settingthan true experimental research designs. It allows researchers to evaluate the impact of quasi-independent variables under naturally occurringconditions. It may be able to establishing casual relationship.Wherein some of the hypotheses are practically answeredthrough this design
  41. 41. DISADVANTAGES OF QUASI-EXPERIMENTALDESIGN There is no control over extraneousvariables influencing the dependantvariables. The absence of a control group or lack ofcontrol over the research setting makes theresults of this design less reliable & weak forthe establishment of casual relationshipbetween independent &
  42. 42. PRE –
  43. 43.  This research design is considered very weak, becausethe researcher has very little control over the experimentTYPES OF PRE-EXPERIMENTAL RESEARCH DESIGN:o One-shot case designo One-group pretest-posttest
  44. 44. ONE-SHOT CASE DESIGN In this research design, a singleexperimental group is exposed to atreatment & observations are made after theimplementation of that treatment. There is no random assignment of subjectsto the experimental group & no controlgroup at all.www.drjayeshpatidar.blogspot.comExp. group Treatment Post-test
  45. 45. ONE-GROUP PRETEST-POSTTEST DESIGN It is the simplest type of pre-experimental design, whereonly the experimental group is selected as the studysubjects. A pretest observation of the dependant variables ismade before implementation of the treatment to theselected group, the treatment is administered, & finally aposttest observation of dependant variables is carriedout to assess the effect of treatment on the group. Some researcher also argue this design as sub type ofquasi-experimental research design. However inabsence of both randomization & control group. This design ethically can not be placed under theclassification of quasi-experimental research
  46. 46. COUNT…www.drjayeshpatidar.blogspot.comExp. group Pretest Treatment Post-test
  47. 47. ADVANTAGES OF PRE-EXPERIMENTAL DESIGN:o Very simple & convenient to conduct these studies in naturalsettings, especially in nursing.o Most suitable design for the beginners in the field ofexperimental research.DISADVANTAGES OF PRE-EXPERIMENTAL DESIGN:o Considered a very weak experimental design to establishcasual relationship between independent & dependantvariables, because it controls no threat to internal validity.o It has very little control over the research.o It has a higher threat to internal validity of research, & mayhave a selection bias, which can be very serious threats for inusing this particular
  48. 48.