This document discusses different types of experimental research designs, including their advantages and disadvantages. It covers true experimental designs like pretest-posttest and Solomon four-group designs. It also discusses quasi-experimental designs like nonequivalent control group and time series designs, as well as pre-experimental designs. Threats to internal and external validity are explained for different designs.
Experimental Research Design - Meaning, Characteristics and ClassificationSundar B N
This ppt contains Experimental Research Design Which covers Meaning, Characteristics and Classification of Experimental Research Design.
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Experimental Research Design - Meaning, Characteristics and ClassificationSundar B N
This ppt contains Experimental Research Design Which covers Meaning, Characteristics and Classification of Experimental Research Design.
Subscribe to Vision Academy
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In this ppt the viewer will able to know about Types of Experimental Design. During the research design what kind of experimental design is applicable? Why experimental design needed in experimental research. Experimental research is research conducted with a scientific approach using two sets of variables. The first set acts as a constant, which you use to measure the differences of the second set. (Example: Temperature & Time in reactor)
Portion explained:
1. Definition of Experimental research
2. Situations to conduct Experimental Research
3. Types of experimental research design
4. Pre-experimental research design
5. True experimental research design
6. Quasi-experimental research design
7. Advantages of experimental research
PowerPoint presentation created for graduate course in Research Methodologies. Very wordy and not my usual style, but had too much information to include to do much style-wise.
In this ppt the viewer will able to know about Types of Experimental Design. During the research design what kind of experimental design is applicable? Why experimental design needed in experimental research. Experimental research is research conducted with a scientific approach using two sets of variables. The first set acts as a constant, which you use to measure the differences of the second set. (Example: Temperature & Time in reactor)
Portion explained:
1. Definition of Experimental research
2. Situations to conduct Experimental Research
3. Types of experimental research design
4. Pre-experimental research design
5. True experimental research design
6. Quasi-experimental research design
7. Advantages of experimental research
PowerPoint presentation created for graduate course in Research Methodologies. Very wordy and not my usual style, but had too much information to include to do much style-wise.
Experimental ProceduresThe specific experimental design procedur.docxgitagrimston
Experimental Procedures
The specific experimental design procedures also need to be identified. This discussion involves indicating the overall experiment type, citing reasons for the design, and advancing a visual model to help the reader understand the procedures.
• Identify the type of experimental design to be used in the proposed study. The types available in experiments are pre-experimental designs, quasi-experiments, true experiments, and single-subject designs. With pre-experimental designs, the researcher studies a single group and provides an intervention during the experiment. This design does not have a control group to compare with the experimental group. In quasi-experiments, the investigator uses control and experimental groups but does not randomly assign participants to groups (e.g., they may be intact groups available to the researcher). In a true experiment, the investigator randomly assigns the participants to treatment groups. A single-subject design or N of 1 design involves observing the behavior of a single individual (or a small number of individuals) over time.
• Identify what is being compared in the experiment. In many experiments, those of a type called between-subject designs, the investigator compares two or more groups (Keppel & Wickens, 2003; Rosenthal & Rosnow, 1991). For example, a factorial design experiment, a variation on the betweengroup design, involves using two or more treatment variables to examine the independent and simultaneous effects of these treatment variables on an outcome (Vogt, 2011). This widely used behavioral research design explores the effects of each treatment separately and also the effects of variables used in combination, thereby providing a rich and revealing multidimensional view. In other experiments, the researcher studies only one group in what is called a within-group design. For example, in a repeated measures design, participants are assigned to different treatments at different times during the experiment. Another example of a within-group design would be a study of the behavior of a single individual over time in which the experimenter provides and withholds a treatment at different times in the experiment to determine its impact.
• Provide a diagram or a figure to illustrate the specific research design to be used. A standard notation system needs to be used in this figure. A research tip I recommend is to use a classic notation system provided by Campbell and Stanley (1963, p. 6):
X represents an exposure of a group to an experimental variable or event, the effects of which are to be measured.
O represents an observation or measurement recorded on an instrument.
Xs and Os in a given row are applied to the same specific persons. Xs and Os in the same column, or placed vertically relative to each other, are simultaneous.
The left-to-right dimension indicates the temporal order of procedures in the experiment (sometimes indicated with an ...
Comparing research designs fw 2013 handout versionPat Barlow
This is an updated version of my Comparing Research Designs lecture, which now includes discussions on: (1) common considerations with research design such as bias, reliability, validity, and confounding; and (2) expanded discussion of RCT designs including factorial and cross-over designs.
Research Methods in PsychologyQuasi-Experimental Designs.docxaudeleypearl
Research Methods in Psychology
Quasi-Experimental Designs
1
Characteristics of True Experiments
Manipulate Independent Variable (IV)
Treatment, comparison conditions
High degree of control
Choice of the DVs
Random assignment to conditions
Unambiguous outcome regarding effect of IV on DV
Internal validity
2
Applied Research
Goals
Test external validity of lab findings
Improve conditions in which people live and work (natural settings)
Quasi-experiments
Procedures that approximate the conditions of highly controlled laboratory experiments
3
Permission
Difficult to gain permission to conduct true experiments in natural settings
Difficult to gain access to participants
Random assignment perceived as unfair
People want a “treatment”
Random assignment is best way to determine whether a treatment is effective
Use “waiting-list” control group or alternate treatments
Tablets in English and science classes example
Obstacles to Conducting True Experiments in Natural Settings
4
Advantage of True Experiments
Threats to internal validity are controlled
8 general threats to internal validityhistoryregressionmaturationselectiontestingsubject attritioninstrumentationadditive effects with selection
5
Threats to Internal Validity
History
When an event occurs at the same time as the treatment and changes participants’ behavior
Participants’ “history” includes events other than treatment
Difficult to infer treatment has an effect
6
History Threat, continued
Does a campus recycling awareness campaign influence the amount of paper, plastic, and cans in campus bins?
History threat: Suppose at week 4 (X = treatment) a popular celebrity also starts to promote recycling in the media.
Can you conclude the campus campaign was effective?
7
Series 1 1 2 3 4 X 5 6 7 8 30 35 30 35 40 55 55 60 55
Week
Recycling (Kg)
Threats to Internal Validity, continued
Maturation
Participants naturally change over time.
These maturational changes, not treatment, may explain any changes in participants during an experiment.
8
Maturation Threat, continued
Does a new reading program improve 2nd graders’ reading comprehension?
Reading comprehension improves naturally as children mature over the year.
Can you conclude the reading program was effective?
9
Series 1 Pre Post 25 70
Reading Comprehension
Threats to Internal Validity, continued
Testing
Taking a test generally affects subsequent testing.
Participants’ performance on a measure at the end of a study may differ from an initial testing because of their familiarity with the measure.
10
Testing Threat, continued
Does teaching a new problem solving strategy influence people’s ability to solve problems quickly?
If similar problems are used in the pretest, faster problem solving at post-test may be due to familiarity with the test.
Can we conclude the new strategy improves problem-solving ability?
11
Series 1 Pre Post 12 4
Minutes (Mean)
Threats to Internal Validity, continued
Ins ...
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
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The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
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Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
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Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
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TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
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These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
2. Experimental research answers the question “What if?” The researcher manipulates independent variables (e.g., type of treatment, teaching method, communication strategy) and measures dependent variables (anxiety level, English comprehension, s atisfaction) in order to establish cause-and-effect relationships between them. The independent variable is controlled or set by the researcher. The dependent variable is measured by the researcher. An “experiment” is a prescribed set of conditions which permit measurement of the effects of a particular Treatment.
3. Threats to experimental research Internal validity Internal invalidity asks the question, “Are the measurements I make on my dependent (i.e., the variable I measure) variable influenced only by the treatment, or are there other influences which change it?” External validity To how much the results are generalized to target population.
4. Internal validity History, Maturation, Testing, Instrumentation, Statistical regression, Differential selection, Experimental mortality, And selection-maturation interaction. The John Henry effect and experimental treatment diffusion.
5. History History refers to events other than the treatment that occur during the course of an experiment which may influence the post-treatment measure of treatment effect. If the explosion of the nuclear reactor in Chernobyl, Ukraine had occurred in the middle of a six-month treatment to help people reduce their “anxiety of nuclear power,” Must occur during the experiment. Controlled be control group
6. Maturation Subjects change over the course of an experiment. These changes can be physical, mental, emotional, or spiritual. Perspective can change. The natural process of human growth can result in changes in post-test scores quite apart from the treatment. Question: How would a “control group” control this source of internal invalidity
7. Testing A common research design is to give a group a pre-test, a treatment, and then a post-test . If the same test is used both times, the group may show an improvement simply because of their experience with the test. This is especially true when the treatment period is short and the tests are given within a short time.
8. Instrumentation If you use different tests for pre- and post-measurements, then the change in pre- and post-scores may be due to differences between the tests rather than the treatment. The best remedy is to use randomization and a post-test only design.
9. Statistical regression Statistical regression refers to the tendency of extreme scores, whether low or high, to move toward the average on a second testing. Subjects who score very high or very low on one test will probably score less high or low when they take the test again. That is, they regress toward the mean. Do not study groups formed from extreme scores. Study the full range of scores.
10. Differential selection If we select groups for “treatment” and “control” differently, then the results may be due to the differences between groups before treatment. Randomization solves this problem by statistically equating groups.
11. E xperimental mortality Experimental mortality, also called “attrition,” refers to the loss of subjects from the experiment. If there is a systematic bias in the subjects who drop out, then posttest scores will be are biased. For example, if subjects drop out because they are aware that they’re not improving as they should, then the post-test scores of all those who complete the treatment will be positively biased. Your results will appear more favorable than they really are. How does use of a control group solve the problem of attrition?
12. Selection-Maturation Interaction of Subjects Interaction means the mixing or combining of separate elements. If you draw a group of subjects from one school to serve as the treatment group, and a second group from a different schools to serve as a control, you could well find -- beyond the simple problem of selection differences (“Are the two groups equivalent?”) -- a mixing of selection and maturation factors to compound the extraneous influence on your measurements. For example, if the two schools differ in the average age of their members, they may well respond to the treatment differently due to inherent maturational factors. Randomly selecting all subjects from a defined population solves this problem.
13. The John Henry Effect John Henry, the legendary “steel drivin’ man,” set himself to prove he could drive railroad spikes faster and better than the newly invented steam-powered machine driver. He exerted himself so much in trying to outdo the "experimental" condition that he died of a ruptured heart. If subjects in a control group find out they are in competition with those in an experimental treatment, they tend to work harder. When this occurs, differences between control and treatment groups is decreased, minimizing the perceived treatment effect.
14. Treatment diffusion Similar to the John Henry effect is treatment diffusion. If subjects in the control group perceive the treatment as very desirable, they may try to find out what’s being done. Both the John Henry Effect and Treatment Diffusion can be controlled if experimental and control groups are isolated.
15.
16. Reactive effects of testing Subjects in your samples may respond differently to experimental treatments merely because they are being tested. Since the population at large is not tested, experimental effects may be due to the testing procedures rather than the treatment itself. This reduces generalizability. One type of reactive effect is pretest sensitization. Another type of reactive effect is post-test sensitization. The posttest can be, in itself, a learning experience that helps subjects to “put all the pieces together.” Different results would be obtained if the treatment were given without a posttest. While researchers must make measurements, care must be taken to measure treatment effect, not add to it, with a post-test.
17. Treatment and Subject Interaction Subjects in a sample may react to the experimental treatment in ways that are hard to predict. This limits the ability of the researcher to generalize findings outside the experiment itself. If there is a systematic bias in a sample, then treatment effects may be different when applied to a different sample.
18. Testing and Subject Interaction Subjects in a sample may react to the process of testing in ways that are hard to predict. This limits the ability of the researcher to generalize findings outside the experiment itself. If there is a systematic bias of test anxiety or “test-wiseness” in a sample, then treatment effects will be different when applied to a different sample
19. Multiple Treatment Effect Normally we find a single treatment in an experiment. If, however, an experiment exposes subjects to, say, three treatments (A, B, and C) and test scores show that treatment C produced the best results, one cannot declare treatment C the best. It may have been the combination of the treatments that led to the results. Treatment C, given alone, may produce different results.
20.
21.
22. True Experimental group Design Advantages of the true-experimental design include: Greater internal validity Causal claims can be investigated Disadvantages: Less external validity (not like real world conditions) Not very practical True Experimental Designs Experimental designs are considered true experiments when they employ randomization in the selection of their samples and control for extraneous influences of variation on the dependent variable. The three designs we will consider in this section are the best choices for an experimental dissertation. These are the pretest-posttest control group design, the Posttest Only Control Group design, and the Solomon Four Group design.
23. Quasi-experimental Design Without proper randomization Lack of rigorous statistical scrutiny Some advantages of the quasi-experimental design include: Greater external validity (more like real world conditions) Much more feasible given time and logistical constraints Disadvantage: Not as many variables controlled (less causal claims)
24. Pre-experimental Design Lacking in several areas of the true-experimental criteria. No random selection in most of the cases. Employment of just single group that receives treatment, no control group. The advantages are: Very practical Set the stage for further research Disadvantages: Lower validity
25. True Experimental Design The posttest only control group design. The pretest posttest control group design. The Solomon four group control design.
27. Pre-experimental Design The one-shot case study One group Pretest Posttest study The static group comparison study
28. If there is only one independent variable that can be manipulated, then a single-variable design is used. If there are two or more independent variables, and at least one can be manipulated, then a factorial design should be chosen.
29. Single-variable designs. These studies are classified under three main headings depending on the degree of control maintained on other variables: 1. Pre-experimental designs (low degree of control) 2. True experimental designs (high degree of control) 3. Quasi-experimental designs (medium degree of control)
30.
31. One-shot case studies: One group is exposed to the treatment, and only a posttest is given to observe or measure the effect of the treatment on the dependent variable within the experimental group. Since it is applied on a single group, there is no control group involved in this design. First of all, the chosen group is exposed to the treatment , and then it is tested only once for the purpose of measuring the degree of change on the dependent variable after the treatment.
32. One-group pretest-posttest design: One group is pretested and exposed to the treatment, and then posttested. This is called a one-group pretest-posttest design because the two tests are administered to the same group. The first one is administered at the beginning of the treatment and the second one at the end.
33. Static-group comparison design At least two groups are involved. After one group receives the treatment, all groups are posttested. This design has better control over most of the variables
34.
35. True experimental designs Have the highest level of control among the three single-variable experimental designs because the subjects within the groups are randomly assigned for each group . When subjects are randomly assigned, there is higher control of the internal validity as well as the external validity. Moreover, there is always a control group to compare the results of the subjects in the experiment with other subjects of similar status that have not been exposed to the treatment.
36. True experimental research may be designed with or without a pretest on at least two groups of randomly assigned subjects. The classification of true experimental designs is made accordingly : 1. The posttest-only control group design 2 .The pretest-posttest control group design 3. Solomon four-group design
37. Posttest Only Control Group Subjects are randomly selected and assigned to two groups. Due to randomization, the two groups are statistically equal. No pretest is given. One group receives the Treatment R X O 1 R O2 Example. Third graders are randomly assigned to two groups. Then one group receives a special study on the life of Iqball. Both are tested on their knowledge of Iqball at the conclusion of the study. Analysis. The difference between group means (O1 and O2) can be computed by an independent groups t-test.
38.
39. Pretest-Posttest Control Group Two randomly selected groups are measured before (O1 and O3) and after (O2 and O4) one of the groups receives a treatment (X). R O 1 X O 2 R O3 O4 Example. Third graders are randomly assigned to two groups and tested for knowledge of Arithmetic. Then one group gets a special study on Arithmetic. Both are then tested again.
40.
41. Analysis. The t-test for independent samples (Chapter 20) can be used to determine if there is a significant difference between the average scores of the groups (O2 and O4). You can also compute gain scores (O2 - O1 and O4 - O3) and test the significance of the average gain scores with the matched samples t-test. This design’s only weakness is pre-test sensitization and the possible interaction between pretest and treatment.
42. Solomon four-group design Takes the effect of pretest and posttest sensitivization into consideration. It is the combination of pretest-posttest control group (G1 and G2) and posttest only control group (G3 and G4) designs. In this case, subjects are randomly selected and placed into four groups;
43.
44. Example. Third graders are randomly assigned to 1 of 4 groups. The “knowledge of language” is measured in groups 1 and 2. Groups 1 and 3 are given a special study on the language learning. When the special study is over, all four groups are tested. Analysis. One-way ANOVA can be used to test the differences in the four posttest mean scores (O2, O4, O5, O6). The effects of the pretest can be analyzed by applying a t-test to the means of O4 (pretest but no treatment) and O6 (neither pretest or treatment). The effects of the treatment can be analyzed by applying a t-test to the means of O5 (treatment but no pretest) and O6 (neither pretest or treatment). Subject maturation can be analyzed by comparing the combined means of O1 and O3 against O6.
45. - the first and the second groups are retested; - the first and the third groups are exposed to the treatment, and the second and the fourth groups are taken as control groups; - all four groups are posttested. This design provides the best result but it requires a large sample so that enough subjects could be assigned to four groups. When the sample is large, administering the tests becomes difficult, time and energy consuming.
46. Quasi-experimental Designs The term quasi- (pronounced kwahz-eye) means almost, near, partial, pseudo, or somewhat . Quasi-experimental designs are used when true experiments cannot be done. A common problem in educational research is the unwillingness of educational administrators to allow the random selection of students out of classes for experimental samples. Without randomization, there are no true experiments. So, several designs have been developed for these situations that are “ almost true experiments,” or quasi-experimental designs. We’ll look at three: the time series, the nonequivalent control group design, and the counterbalanced design.
47. Time Series Establish a baseline measure of subjects by administering a series of tests over time (O1 through O4 in this case). Expose the group to the treatment and then measure the subjects with another series of tests (e.g., O5 through O8). O1 O2 O3 O4 X O5 O6 O7 O8 Comments. Since there is no control group, one cannot determine the effects of history on the test scores. Instrumentation may also be a problem (Are the tests equivalent?) the reactive effects of repeated testing of subjects is a source of external invalidity.
48. Nonequivalent Control Group Design Subjects are tested in existing or “intact” groups rather than being randomly selected. The dotted line in the diagram represents “non-equivalent” groups. Both groups are measured before and after treatment. Only one group receives the treatment. O 1 X O 2 --------------------- O3 O4 Comments. This design should be used only when random assignment is impossible. It does not control for selection-maturation interaction statistical regression. pretest sensitization.
49. Counterbalanced Design Subjects are not randomly selected, but are used in intact groups. Group 1 receives treatment 1 and test 1. Then at a later time, they receive treatment 2 and test 2. Group 2 receives treatment 2 first and then treatment one. Time 1 2 Group1 X1 O X2 O Group2 X2 O X1 O Example. Two third grade classes receive two special studies on language: one in classroom and the other on a computer. Class 1 does the classroom work first, followed by the computer; class 2 does the computer work first. Both groups are tested after both treatments.
50. Analysis. Use the Latin Squares analysis (beyond the scope of this text). Comments. Since randomization is not used in this design, selection-maturation interaction may be a problem. Multiple treatment effect is a possible source of external invalidity.