Experimental Studies

Sherwan Najmaldin Noori Student No. (20143744) Suppervised by: Asst. Prof. Dr. Cise Cavusoglu

NEAR EAST UNIVERSITYFACULTY : EDUCATION SCIENCES INSTITUTE DEPARTMENT: ENGLISH LANGUAGE TEACHING

experiment is a study in which a treatment, procedure, or program is intentionally introduced and a result or outcome is observed.An experimental study is a type of evaluation that seeks to determine whether a program or intervention had the intended causal effect on program participants.

Experimental Study

Experimental design is a blueprint of the procedure that enables the researcher to test his hypothesis by reaching valid conclusions about relationships between independent and dependent variables.

Experimental Design

Types of experimental design

The "One-Shot Case Study"

No control group. This design has virtually no internal or external validity.

2 Group, Post-test Comparison

The main advantage of this design is randomization. The post-test comparison with randomized subjects controls for the main effects of history, maturation, and pre-testing; because no pre-test is used there can be no interaction effect of pre-test and X. Another advantage of this design is that it can be extended to include more than two groups if necessary.

Treatment Post-testX O

Treatment Post-testX O O

One group Pre-test, Post-test

Pre-test Treatment Post-testO X O

Minimal Control. There is somewhat more structure, there is a single selected group under observation, with a careful measurement being done before applying the experimental treatment and then measuring after. This design has minimal internal validity, controlling only for selection of subject and experimental mortality. It has no external validity.

Two groups, Nonrandom Selection, Pre-test, Post-test

Group Pre-test Treatment Post-testExperimental group = E

O X O

Control Group = C O O

The main weakness of this research design is the internal validity is questioned from the interaction between such variables as selection and maturation or selection and testing. In the absence of randomization, the possibility always exists that some critical difference, not reflected in the pretest, is operating to contaminate the posttest data.

Two groups, Random Selection, Pre-test, Post-test

Group Pre-test Treatment Post-testExperimental group = E (R)

O X O

Control Group =C (R)

O O

The advantage here is the randomization, so that any differences that appear in the posttest should be the result of the experimental variable rather than possible difference between the two groups to start with. This is the classical type of experimental design and has good internal validity.

Experimental research is an attempt by the researcher to maintain control over all factors that may affect the result of an experiment. In doing this, the researcher attempts to determine or predict what may occur.

Experimental Research

• Select a topic• Review the relevant literature and define a research

question• Develop a research hypothesis• Select and assign participants to groups• Select measurement instruments• Define and administer experimental treatments• Collect and analyze data• Make a decision about the hypothesis• Formulate conclusions

Steps in Planning and 5ing Experimental Research

As with other research methods, the experimental researcher bases the topic selection on personal interest, experience, and an initial review of the literature. Typically in experimental research, the researcher is interested in determining if some treatment causes a significant change in behavior.

Selecting a Topic.

The researcher does an exhaustive literature review to determine the findings of current research on the topic of interest. This means that the researcher examines past literature to determine how others have researched the same topic, what variables or issues were studied, discussed, or both, and what the findings of those studies indicated.

Review the relevant literature and define a research question

A research hypothesis is an educated guess that states the expected outcome of the study. The researcher is “educated” through the literature review. Based on the findings of the literature review, the researcher develops and states a hypothesis that indicates the expected causal relationship between the variables.

Develop a research hypothesis

• Directional Hypothesis States the direction or the expected outcome.

That is, the researcher feels confident enough to suggest which group would outperform the other group(s).

• Non-directional Hypothesis Simply states that there will be some difference

between the variables, but the direction of that difference is not being predicted.

Types of hypothesis in Experimental Study

• Null hypothesis states that no significant difference between the variables is expected after the treatment is

applied. The null hypothesis is implicit in all experimental research. That is, inferential statistics always test the null hypothesis, and in most cases, the researcher hopes to disprove the null hypothesis in favor of the research hypothesis.

Types of hypothesis in Experimental Study

Most experimental studies have at least two groups, often referred to as the experimental and control groups. In an experimental study, the researcher randomly selects and about assigns participants to groups. Random selection allows the researcher to take the findings based on the sample and generalize

those findings back to the entire population.

Select and assign participants to groups

Instruments or measurement tools for an experimental study are selected with the same care and attention as in other types of research. You want to be certain that the instrument you select is an appropriate measure for your dependent variable.

Select measurement instruments

A major part of creating a research proposal is defining the treatments to be administered

to the participants, also known as the research plan. This plan should describe all procedures to be used in the study. Specifically, what happens to the participants in each group? How does the treatment for the experimental group differ from that of the control group?

Define and administer experimental treatments

The data produced by experimental studies are quantitative, the researcher who actually conducts a study examines the data using statistical procedures. The type of statistical analysis depends on the type of data you collected.

Collect and analyze data

The decision made about the hypothesis in an experimental study is based on statistical analysis of a study’s data and forms the basis for the conclusions of a study. Confirming a research hypothesis can add to the body of knowledge on a topic and have practical implications.

Formulate conclusions

The data collected and analyzed will provide either support for your research hypothesis or evidence to the contrary. In general, the researcher wants to reject the null hypothesis, which states that there is no real difference between the treatment groups—in other words, that any difference found was due to chance and not to the experimental treatment.

Make a decision about the hypothesis

Internal validity is the degree to which observed

changes in a dependent variable can be attributed to changes in an independent variable. Asks the question, “ Are the measurements I make on my dependant (i.e. the variable I measure) variable influenced only by the treatment, or are there other influences which change it?”

Threats to Experimental Study

• External Validity External validity has to do with the generalize-ability of the research findings; to what extent can the findings of an experiment or quasi-experiment be generalized to and across various populations, settings, and epochs? To how much the results are generalized to target population.

Threats to Experimental Study

• History• Maturation• Testing• Instrumentation• Statistical regression• Differential selection of subjects• Mortality

Internal Validity Threats

History when changes in the dependent variable are due to some

extraneous event that takes place between pre- and posttest, it makes it difficult to determine whether the results were due to the experimental manipulation (i.e. changes in the independent variable) or to the extraneous event.

How to control: Include an appropriate control group

Internal Validity Threats

Maturation Change in the participant over the course of time, where such

change is not the focus of interest of the research study. This may involve growth (e.g., getting smarter or stronger) or decline (e.g., dementing).

How to control Include an appropriate control group

Internal Validity Threats

Testing The reactive effects of testing where the very act of assessment

influences the variable under investigation. Some measures are highly reactive, whereas other measures are largely un reactive . Also, repeated testing can increase familiarity with the test, which might bias scores.

How to control This threat can be dealt with in various ways, such as by selecting un

reactive measures (e.g., unobtrusive observation) or by including a control group.

Internal Validity Threats

Instrumentation When an effect is due to a change in the measuring instrument from

pre- to posttest rather than due to the manipulation of the independent variable. Instrumentation can affect all forms of measurement, including observers, self-report tools, interview schedules, and devices that measure physiological processes.

How to control Use reliable or valid instrument(s); train observers and use short

observation periods.

Internal Validity Threats

Statistical regression People selected for extreme scores (very high or very low) will

have less extreme scores when they are retested on the same or related variables. Why does regression occur? The farther a score is from the mean, the more extreme it is.

How to control Include a control group selected using same criteria

Internal Validity Threats

Differential selection of subjects When the effects on the dependent variable

arise from differences in the kinds of people in the experimental groups.

How to control Use random assignment to groups; pretest

participants to see if groups are similar

Internal Validity Threats

Mortality or Attrition If a participant with a particular score drops out of the

experimental group, a control group member with a comparable score on the pretest can be eliminated, thereby controlling for mortality or subject attrition.

How to control

Pretest to obtain information for examining who dropped out of one group and eliminate a similar participant from the other group to maintain equivalent groups; maintain contact with both treatment and control groups

Internal Validity Threats

Multiple-treatment interaction Participants are exposed to multiple treatments that are

part of some overarching treatment or simply exposed to more than one treatment; when this occurs, it might be difficult to determine which treatment resulted in any difference that is found, limiting generalizability.

How to control Limit the number of treatments delivered, or deliver

different treatments at different times; if one treatment has many components, establish comparison groups receiving different components.

External Validity Threats

Pretest-treatment interaction Pretest sensitizes participants to the treatment, and

outcome would be different if the participants had not been pretested.

How to control Include appropriate control groups who also receive

pretests and a treatment group that receives no pretest.

External Validity Threats

Bartlett, F. (1995). Remembering : a study in experimental and social psychology. Cambridge New York: Cambridge University Press.

Brachit, G. H., Glass, G. V. (1968) The External Validity of Experiments. American Educational Research Journal, 5(4) 437-474.

Lodico, M., Spaulding, D., & Voegtle, K. (2006). Methods in educational research: From theory to practice. San Francisco: Jossey Bass.

Markstein, G. H. (2012). Experimental and theoretical studies of flame-front stability. Journal of the Aeronautical Sciences (Institute of the Aeronautical Sciences), 18(3).

Wind Goodfriend: True Experimental Design. (n.d.). Education Portal Web site. Retrieved from http://education-portal.com/academy/lesson/true-experimental-design.html#lesson.

References

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