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Research Design Used in Experimental Hypothesis Testing

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  1. 1. EXPERIMENTAL RESEARCH DESIGN MR. JAYESH PATIDAR www.drjayeshpatidar.blogspot.com
  2. 2. INTRODUCTION…  Experimental is most scientifically sophisticated research method.  It is defined as 'observation under controlled conditions'.  Experimental research design 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), & the effect of those interventions is observed on the dependant variable. www.drjayeshpatidar.blogspot.com
  3. 3. TRUE EXPERIMENTAL DESIGN www.drjayeshpatidar.blogspot.com
  4. 4. CONCEPT… True experimental research designs are those where researchers have complete control over the extraneous variables & can predict confidently that the observed effect on the dependable variable is only due to the manipulation of the independent variable. www.drjayeshpatidar.blogspot.com
  5. 5. ESSENTIAL CHARACTERISTICS…  A true experimental research design must essentially consist of the following three characteristics:  Manipulation  Control  Randomization www.drjayeshpatidar.blogspot.com
  6. 6. MANIPULATION:  Manipulation refers to conscious control of the independent variable by the researcher through treatment or intervention(s) to observe its effect on the dependent variable.  In other words, it is a conscious act by the researcher, where he or she varies the independent variable & observes the effect that manipulation has on the dependant variable of interest. www.drjayeshpatidar.blogspot.com
  7. 7. COUNT…  For example, a researcher is conducting a study on efficacy of cholrhexidine mouthwash on the prevention of ventilator-associated pneumonia (VAP) among patients admitted in ICUs.  In this example, chlorhexidine mouthwash is the dependent variable, which is manipulated by the researcher, & is used as an intervention for the experimental group, while the control group is kept deprived of it to observe its effect on the incidence of VAP. www.drjayeshpatidar.blogspot.com
  8. 8. CONTROL:  Control is another essential element of true experimental design.  Control refers to use of control group & controlling the effects of extraneous variables on the dependent variable in which researcher is interested.  The subject in the control & experimental groups are similar in number & characteristics, but the subject in the control group receive no experimental treatment or any intervention at all. www.drjayeshpatidar.blogspot.com
  9. 9. COUNT…  The experimental group receives the planned treatment or intervention & a comparison is made with the control group to observe the effect of this treatment or intervention.  Generally in health care & nursing research, it is not ethically feasible keep a control group deprived of interventions; however, existing conventional method of interventions may be compared with experimental interventions. www.drjayeshpatidar.blogspot.com
  10. 10. RANDOMIZATION:  Randomization means that every subject has an equal chance of being assigned to experimental or of study subjects on a random basis.  Through random assignment of subject under experimental or control group, chances of systemic bias is eliminated.  Randomization is used in true experimental research design to minimize the threat of internal validity of the study & to eliminate the effect of extraneous variables on dependent variables.  Through randomization, on average the characteristics of the subject in experimental & control groups are similar, thus influence of extraneous variables on dependant variable is eliminated by dispersing the variability of the subject characteristics equally in both the groups. www.drjayeshpatidar.blogspot.com
  11. 11. COUNT… METHODS OF RANDOMIZATION:  Random assignment of subject may done with simple flip of a coin for each subject; if coin lands on its 'head', subjects are assigned to first group & with 'tail' subjects are assigned to control group.  Another possible method is to write the names of the subjects on slips of paper & put the slips into a bowl & then draw lots. The first designated numbers of subjects are placed in one group, & rest are assigned under another group.  Thirdly a random table may be used to facilitate the randomization process. In this method, blind-folded subjects choose a number from a table of number horizontally (row) or vertically (columns), till a requisite number is reached for both experimental & control groups. Computer-assisted random sequences also may be used for the random assignment of the subjects www.drjayeshpatidar.blogspot.com
  12. 12. TYPES OF THRUE EXPERIEMNTAL DESIGN www.drjayeshpatidar.blogspot.com True Experiential Design Post-test only Factorial Pretest post-test only Crossover Solomon 4 groups Randomized block
  13. 13. POST-TEST-ONLY CONTROL DESIGN:  Composed of two randomly assigned group, i.e. experimental & control, but neither of which is pretested before the implementation of treatment on the experimental group.  In addition, while treatment is implement on the experimental group only, post-test observation is carried out on both the group to assess the effect of manipulation.  This design can be helpful in situations where it is not possible to pretest the subjects.  For example, to study the effect of an educational intervention related to urinary incontinence on the subsequent help-seeking behavior of older adults. www.drjayeshpatidar.blogspot.com
  14. 14. COUNT… www.drjayeshpatidar.blogspot.com Random assignment Exp. group Treatment Post-test Control group Post-test
  15. 15. PRETEST-POST-TEST-ONLY DESIGN  In this research designs, subjects are randomly assigned to either the experimental pr the control group.  The effect of the dependent variable on both the groups is seen before the treatment (pretest).  Later, the treatment is carried out on experimental group only, & after-treatment observation of dependant variable is made on both the groups to examine the effect of the manipulation of independent variable on dependant variable.  For example, such a design could be used for 'an experimental study to assess the effectiveness of cognitive behavioral therapy interventions for patients with breast cancer.' www.drjayeshpatidar.blogspot.com
  16. 16. COUNT… www.drjayeshpatidar.blogspot.com Random assignment Exp. group Treatment Post- test Control group Post-test pretest pretest
  17. 17. SOLOMON FOUR-GROUP DESIGN  There are two experimental groups (experimental group 1 & experimental group 2) & two control groups (control group 1 & control group 2).  Initially, the investigator randomly assigns subjects to the four groups.  Out of the four groups, only experimental group 1 & control group1 receives the pretest, followed by the treatment to the experimental group 1 & experimental group 2.  Finally, all the four groups receive post-test, where the effects of the dependant variables of the study are observed & comparison is made of the four groups to assess the effect of independent variable (experimental treatment) on the dependant variable. www.drjayeshpatidar.blogspot.com
  18. 18. COUNT…  In this, experimental group 2 was observed at one occasion, & that score should be similar to average scores of those in experimental & control groups.  To estimate the amount of change in experimental & control group 2, the average test scores of experimental & control groups 1 are used as baseline  The solomon four-group design is believed to be most prestigious experimental research design, because it minimizes the threat to internal & external validity. www.drjayeshpatidar.blogspot.com
  19. 19. COUNT… www.drjayeshpatidar.blogspot.com Random assignment Exp. Group 1 Control Group 1 Exp. Group 2 Control Group 2 pretest treatment Post-test pretest Post-test treatment Post-test Post-test
  20. 20. FACTORIAL DESIGN  In factorial design, researcher manipulates two or more independent variables simultaneously to observe their effects on the dependant 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 effect of two different protocols of mouth care on prevention of VAP when performed at different frequencies in a day.  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 in any combination.  The first number (α) refers to the independent variables or the type of experimental treatments, & the second number (β) refers to the level or frequency of the treatment. www.drjayeshpatidar.blogspot.com
  21. 21. COUNT… Frequency of mouth care Protocols of the mouth care Chlorhexidine (α1) Saline (α2) 4 hourly (β1) α1….β1 α2….β1 6 hourly (β2) α1….β2 α2….β2 8 hourly (β3) α1….β3 α2….β3 www.drjayeshpatidar.blogspot.com
  22. 22. RANDOMIZED BLOCK DESIGN  Control of inherent differences between experimental subjects & differences in experimental conditions is one of the difficult problems faced by researcher in biological sciences.  When there are a large number of experimental comparison groups, the randomized block design is used to bring homogeneity among selected different groups.  This is simple method to reduce the variability among the treatment groups by a more homogeneous combination of the subjects through randomized block design. www.drjayeshpatidar.blogspot.com
  23. 23. COUNT…  For example, a researcher wants to examine the effects of three different antihypertensive drugs on patients with hypertension.  In this example, to ensure the homogeneity among the subjects under treatment, researcher randomly places the subjects in homogeneous groups (blocks) like patients with primary hypertension, diabetic patients with hypertension, & renal patients with hypertension . www.drjayeshpatidar.blogspot.com
  24. 24. COUNT… Types of antihypertensive drugs Blocks Patients with primary hypertension (I) Diabetic patients with hyper tension (II) Renal patients with hypertension (III) A A, I A, II A, III B B, I B, II B, III C C, I C, II C, III www.drjayeshpatidar.blogspot.com
  25. 25. CROSSOVER 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'.  This design is more efficient in establishing the highest possible similarity among subjects exposed to different conditions, where groups compared obviously have equal distribution of characteristics.  Through crossover design is considered as an extremely powerful research design, sometimes it is not effective because when subjects are exposed to two different conditions, their responses of the second condition may be influenced by their experience in the first condition. www.drjayeshpatidar.blogspot.com
  26. 26. COUNT…  For example, when we are comparing the effectiveness of the chlorhexidine mouth care protocol on group I & saline mouth care protocol on the subjects of group II.  Later, the treatment is swapped, where group I receives the saline mouth care & group II receives chlorhexidine. In such studies, subjects serve as their own control. www.drjayeshpatidar.blogspot.com Groups Protocols of the mouth care Group I Chlorhexidine (α1) Saline (α2) Group II Saline (α2) Chlorhexidine (α1)
  27. 27. ADVANTAGES OF TRUE EXPERIMENTAL DESIGN  Experimental research designs are considered the most powerful designs to establish the causal relationship between independent & dependant variables.  Where the purpose of research is explanation, causal relationship may be established among the variables by experimentation, especially in studies involving physical objects, where the variables are more easily controlled than in human studies.  In this studies, the controlled environment in which the study is conducted can yield a greater degree of purity in observation. www.drjayeshpatidar.blogspot.com
  28. 28. COUNT…  Conditions not found in a natural setting can be created in an experimental setting, where the independent variable is manipulated by investigator.  In the experimental approach, we can often create conditions in a short period of time that may take years to occur naturally. For example, in genetic studies we can breed strains in very small time, which would take a long time in nature to occur.  When the experiment is conducted in a laboratory, experimental unit, or other specialized research setting, it is removed from the pressure & problems of real-life situations & the researcher can pursue his or her studies in a more leisurely, careful, & concentrated way. www.drjayeshpatidar.blogspot.com
  29. 29. DISADVANTAGES OF TRUE EXPERIMENTAL DESIGN  Most of the times, the results of experimental research designs cannot be replicated in studies conducted on human beings due to ethical problems.  For certain research problems, because of the danger to physical & psychological health of the human subjects, it is not possible to conduct experiments on human beings.  Many of the human variables neither have valid measurable criteria nor instruments to measure them. For example, patient welfare or level of wellness cannot be measured on any scale or by any instrument. In these situations, if a refined experimental design is used, there may be a mismatch of research design & the variable- measuring instruments. www.drjayeshpatidar.blogspot.com
  30. 30. COUNT…  In experimental studies conducted in natural settings like hospitals or community, it is not possible to impose control over extraneous variables.  Another disadvantage of the experimental research design is that it is very difficult to get cooperation from the study participants, because it may involve medical or surgical treatment or intervention, which may make the prospective subjects reluctant to participate in research study. www.drjayeshpatidar.blogspot.com
  31. 31. QUASI – EXPERIMENTAL RESEARCH DESIGN www.drjayeshpatidar.blogspot.com
  32. 32. INTRODUCTION…  Quasi-experimental research design involves the manipulation of independent variable to observe to effect on dependant variable, but it lacks at least one of the two characteristics of the true experimental design; randomization or a control group.  In other words, quasi-experimental designs have an element of manipulation but lack at least one of the other two properties that characterize true experiments; randomization or a control group.  Quasi-experimental designs are generally used to establish the causality (effect of independent variable on dependent variable) in situations where researchers are not able to randomly assign the subjects to groups or for various reasons no control group is available for an experimental study. www.drjayeshpatidar.blogspot.com
  33. 33. MAIN CHARACTERISTICS…  Manipulation of the independent variables to observe the effects on the dependant variables.  Lack of at least one of the two other essential characteristics of the true experiment, i.e. random assignment of subject or a control group.  Quasi-independent variables are used instead of true independent variables. Where independent variable is not manipulates in complete controller situations. www.drjayeshpatidar.blogspot.com
  34. 34. TYPES OF QUASI-EXPERIMENTAL DESIGN Nonrandomized control group design Time-series design www.drjayeshpatidar.blogspot.com
  35. 35. NONRANDOMIZED CONTROL GROUP DESIGN  It is also known as the 'nonequivalent control group design'.  This design is identical to the pretest-posttest control group design, except there is no random assignment of subjects in experimental & control groups.  In this design, experimental & control groups are selected without randomization, & dependent variables are observed in experimental as well as control groups before the intervention.  Later, the experimental group receives treatment & after that posttest observation of dependant variables is carried out for both the groups to assess the effect of treatment on experiment group. www.drjayeshpatidar.blogspot.com
  36. 36. COUNT... www.drjayeshpatidar.blogspot.com Exp. group Control group Pretest Pretest Treatment Post-test Post-test
  37. 37. COUNT…  For example, this method was used to study 'the effects of integrated care on quality of work in nursing homes: a quasi- experiment'.  The purpose of this study was to examine the implementation of integrated care in the nursing home sector, & its effect on the quality of work of the caregivers.  A nonequivalent pretest-posttest control group design was used in this study.  Data was collected by through a questionnaire.  The result showed that the intervention appeared to be one successful on the somatic wards.  The caregivers of these wards were more successful in creating a home-like environment for their residents.  Regarding the effects of the intervention on the quality of work factors, the result included an increase of social support by supervision.  The intervention on the psychosomatic wards was unsuccessful, through the introduction of integrated care on the somatic wards was fairly successful. www.drjayeshpatidar.blogspot.com
  38. 38. TIME-SERIES DESIGN  This design is useful when the experimenter wants to measure 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 of the experiment.  Generally it is a single-subject research, in which the researcher carries out an experiment on an individual or on a small number of individuals, by alternating between administering & then withdrawing the treatment to determine the effectiveness of the intervention. www.drjayeshpatidar.blogspot.com Exp. group O1 O3O2 O3O2O1Treatment
  39. 39. COUNT…  A researcher might assess pain levels of a group of patients with low-back pain. After 3 weeks of pain assessment, subjects are taught special exercises to reduce that pain. During the next 3 weeks, pain levels would again be measured.  Measuring a child's school performance on a weekly basis, & then introducing a new teaching technique. Then again measuring on a weekly basis. www.drjayeshpatidar.blogspot.com
  40. 40. ADVANTAGES OF QUASI-EXPERIMENTAL DESIGN  Quasi-experimental designs are more frequently used because they are more practical & feasible to conduct research studies in nursing, where in the absence of a large sample size, randomization &/ or availability of control groups are not always possible.  This design is more suitable for real-world natural setting than true experimental research designs.  It allows researchers to evaluate the impact of quasi- independent variables under naturally occurring conditions.  It may be able to establishing casual relationship. Wherein some of the hypotheses are practically answered through this design only. www.drjayeshpatidar.blogspot.com
  41. 41. DISADVANTAGES OF QUASI-EXPERIMENTAL DESIGN  There is no control over extraneous variables influencing the dependant variables.  The absence of a control group or lack of control over the research setting makes the results of this design less reliable & weak for the establishment of casual relationship between independent & dependant variables. www.drjayeshpatidar.blogspot.com
  42. 42. PRE – EXPERIMENTAL RESEARCH DESIGN www.drjayeshpatidar.blogspot.com
  43. 43.  This research design is considered very weak, because the researcher has very little control over the experiment TYPES OF PRE-EXPERIMENTAL RESEARCH DESIGN: o One-shot case design o One-group pretest-posttest design www.drjayeshpatidar.blogspot.com
  44. 44. ONE-SHOT CASE DESIGN  In this research design, a single experimental group is exposed to a treatment & observations are made after the implementation of that treatment.  There is no random assignment of subjects to the experimental group & no control group at all. www.drjayeshpatidar.blogspot.com Exp. group Treatment Post-test
  45. 45. ONE-GROUP PRETEST-POSTTEST DESIGN  It is the simplest type of pre-experimental design, where only the experimental group is selected as the study subjects.  A pretest observation of the dependant variables is made before implementation of the treatment to the selected group, the treatment is administered, & finally a posttest observation of dependant variables is carried out to assess the effect of treatment on the group.  Some researcher also argue this design as sub type of quasi-experimental research design. However in absence of both randomization & control group.  This design ethically can not be placed under the classification of quasi-experimental research design. www.drjayeshpatidar.blogspot.com
  46. 46. COUNT… www.drjayeshpatidar.blogspot.com Exp. group Pretest Treatment Post-test
  47. 47. ADVANTAGES OF PRE-EXPERIMENTAL DESIGN: o Very simple & convenient to conduct these studies in natural settings, especially in nursing. o Most suitable design for the beginners in the field of experimental research. DISADVANTAGES OF PRE-EXPERIMENTAL DESIGN: o Considered a very weak experimental design to establish casual relationship between independent & dependant variables, 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, & may have a selection bias, which can be very serious threats for in using this particular design. www.drjayeshpatidar.blogspot.com
  48. 48. Thank You www.drjayeshpatidar.blogspot.com

Research Design Used in Experimental Hypothesis Testing

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