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# The experimental method

## by Jessica , Student on Oct 05, 2010

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Mata Kuliah Research Methodology

Mata Kuliah Research Methodology

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## The experimental methodPresentation Transcript

• The Experimental Method
Group 2
Jessica
Junita Kirana
Neli Anastasia
• The Experimental Method
The experimental method involves manipulating one variable to determine if changes in one variable cause changes in another variable. This method relies on controlled methods, random assignment and the manipulation of variables to test a hypothesis.
• Variables
• What are variable?
Variables are things that we measure, control, or manipulate in research. They differ in many respects, most notably in the role they are given in our research and in the type of measures that can be applied to them.
• Types
Descriptive variables are those that which will be reported on, without relating them to anything in particular.
Categorical variables result from a selection from categories, such as 'agree' and 'disagree'.
Numeric variables give a number, such as age.
Discrete variables are numeric variables that come from a limited set of numbers. They may result from , answering questions such as 'how many', 'how often', etc.
Continuous variables are numeric variables that can take any value, such as weight.
• Measurement Scales
A Nominal scale is The lowest measurement level you can use, from a statistical point of view, such as sex and eye colour.
An ordinal scale is next up the list in terms of power of measurement.The simplest ordinal scale is a ranking.
Interval scaleto rank order, quantify and compare the sizes. For example, when we measure temperature (in Fahrenheit), the distance from 30-40 is same as distance from 70-80.
A ratio scale is the top level of measurement and is not often available in social research.The factor which clearly defines a ratio scale is that it has a true zero point.The simplest example of a ratio scale is the measurement of length (disregarding any philosophical points about defining how we can identify zero length).
• Independence
An independent variable is one is manipulated by the researcher. It is like the knob on a dial that the researcher turns. In graphs, it is put on the X-axis.
A dependent variable is one which changes as a result of the independent variable being changed, and is put on the Y-axis in graphs.
Variables may have the following characteristics:
• Period: When it starts and stops.
• Pattern: Daily, weekly, etc.
• Detail: Overview through to 'in depth'.
• Latency: Time between measuring dependent and independent variable (some things take time to take effect).
• Samples
• What is samples?
A sample is a finite part of a statistical population whose properties are studied to gain information aboutthe whole(Webster, 1985). When dealing with people, it can be defined as a set of respondents(people) selected from a larger population for the purpose of a survey.
• Types of samples
The convenient sampleis aconvenience sample results when the more convenient elementary units are chosen from a population for observation.
The judgementsampleisajudgement sample is obtained according to the discretion of someone who is familiar with the relevant characteristics of the population.
The random samplethis may be the most important type of sample. A random sample allows a known probability that each elementary unit will be chosen.
• Populations
• What is populations?
All cases, situations, or individuals who share one or more characteristics.
• Types of populations
TARGET POPULATIONrefers to the ENTIRE group of individuals or objects to which researchers are interested in generalizing the conclusions. The target population usually has varying characteristics and it is also known as the theoretical population.
ACCESSIBLE POPULATION is the population in research to which the researchers can apply their conclusions. This population is a subset of the target population and is also known as the study population.
• Basic Principles of Experimental Designs
• What is Basic Principles of Experimental Designs?
The basic principles of experimental designs are randomization, replication and local control. These principles make a valid test of significance possible. Each of them is described briefly in the following subsections.
Randomization. The first principle of an experimental design is randomization, which is a random process of assigning treatments to the experimental units.The purpose of randomization is to remove bias and other sources of extraneous variation, which are not controllable. Another advantage of randomization (accompanied by replication) is that it forms the basis of any valid statistical test.
• Replication. The second principle of an experimental design is replication; which is a repetition of the basic experiment. In other words, it is a complete run for all the treatments to be tested in the experiment.
Local Control. It has been observed that all extraneous sources of variation are not removed by randomization and replication.For this purpose, use of local control, a term referring to the amount of balancing, blocking and grouping of the experimental units.Balancing means that the treatments should he assigned to the experimental units in such a way that the result is a balanced arrangement of the treatments. Blocking means that like experimental units should be collected together to form a relatively homogeneous group.
• The Difference
• Pre-experimental designs include:
case study design
one group pre-test/post-test design
static group comparison design (cross-sectional study)
• Quasi-experimental designs include:
time series design (may include panel design)
equivalent time samples design-equivalent materials design
nonequivalent control group (comparison group) design
counterbalanced design
separate sample pre-test/post-test design
separate sample pre-test/post-test control group design
multiple time-series design
recurrent institutional cycle design
regression/discontinuity analysis
• True experimental designs include:
pre-test/post-test control group design
Solomon four-group design
post-test only control group design
• Conclusion
The formal experiment and its variants, the pre-experiment and quasi-experiment, are important research tools in language study, and they have added significantly to our knowledge of language leraning, teaching and use.