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Rekabentuk Kajian Eksperimental
Norlena Salamuddin
Selamat Datang ke GGGB6013
Kaedah Penyelidikan I
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Rekabentuk Kajian Eksperimental
Penyelidik mempunyai kawalan ke atas
kajian dari aspek pemilihan sampel,
rawatan yang diberikan, persekitaran,
dsb
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Research
True Experimental
Quasi-Experimental
Ex Post Facto (Causal-Comparative)
Jenis-jenis.
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Ciri-ciri Kajian
Eksperimental Benar Terdapat kumpulan kawalan atau perbandingan
Subjek diagih secara rawak
Rawatan diberi secara rawak kepada kumpulan
Sering digunakan dalam psikologi, perubatan,
pendidikan, dsb
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Ciri-ciri Kajian Kuasi
Eksperimental
Terdapat kumpulan kawalan atau perbandingan
Kumpulan sedia ada digunakan Rawatan diberi secara rawak kepada kumpulan
Dilaukan dalam persekitaran natural
Sering digunakan dalam ekonomi, sosiologi,pentadbiran awam, perancangan bandar dan
wilayah, sains politik, dsb
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Ciri-ciri KajianEx Post Facto
Terdapat kumpulan kawalan atau perbandingan
Kumpulan sedia ada digunakan
Kawalan tidak dimanipulasi, tetapi telah berlaku
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Lakaran Kajian
Untuk ilustrasi rekabentuk kajian, beberapa
simbol digunakan:X1= Rawatan
X2= Kumpulan kawalan
O = Pemerhatian/Cerapan (pra- atau pos-ujian)R = Pemilihan/Agihan rawak
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Sampel Rekabentuk Kajian
Single-Group Pretest-Treatment-
Posttest Design
R O X1O Ini bermaksud, subjekdipilih secara rawak kepada
kumpulan, diberi pra-ujian,kemudian diberi rawatan,
kemudian diberi pos-ujian.
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R O X1O
This is not really an experimental designbecause there is no control group
It is often referred to as a preexperimental design
Novice researchers often use this researchdesign
There are some major problems with thisdesigndid the treatment really make the
difference or was something else happening.
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R O X1O
What are the threats to the Internal
Validity of this type of research (Did
the treatment really cause a
difference?)
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Internal Validity Threats
History
Another event occurs during the time of theexperiment that might cause the difference
An experiment to heighten racial awareness wasconducted by a researcher during February. This isBlack History month; so the results might be affected
by events that occur during Black History month andnot the treatment.
R O X1O
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Internal Validity Threats
Maturation
People naturally change and evolve over time.This may cause the difference.
A college develops a new housing plan to promotemore open-mindness and acceptance of others. Thestudents are tested when they enter college and when
they graduate. The results show they are now moreopen-minded and tolerant of others. Did the housingplan work or do students just mature and grow as aresult of the college experience.
R O X1O
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Internal Validity Threats
Mortality
Some people drop out during an experiment. Thismay affect the outcome.
I am teaching a new experimental seminar on studyskills. About half of the class stopped coming to theseminar before the semester was over. The students
who remained improved their study skills. So mycourse was effective!
Probably not. The half that stopped coming might nothave gained anything; that is why they stoppedattending.
R O X1O
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Internal Validity Threats
Testing
Whenever you give a pretest, the students mayremember the test questions, and get them correcton the posttest.
I gave a test to my study skills group on Monday,presented some unique concepts on Tuesday, then gave
them the posttest on Wednesday. The grades weresignificantly higher on the posttest.
It is possible the grades were higher because the studentsstill remembered the questions from the pretest.
R O X1O
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Internal Validity Threats
Instrumentation
To overcome the testing threat to internalvalidity, a researcher develops a different form ofthe test instrument, but it is not really equivalent.
I gave a test to my study skills group on Monday,presented some unique concepts on Tuesday, then gave
them an alternative form of the pretest on Wednesday.The grades were significantly higher on the posttest.
It is possible the grades were higher because the secondtest was easier than the first.
R O X1O
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Internal Validity Threats
Regression
When subjects are selected because of extremescores on some type of instrument, there istendency for their scores to move more towardthe average on subsequent tests.
An experimenter selected students for a reading
program based on their low test scores. At the end ofthe treatment, the test scores had improved.
Extreme scores naturally move toward the mean onsubsequent tests.
RO X1O
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How to Handle Internal
Validity Threats
Have a control group and use
randomization.This design is the Two-Group Pretest-Treatment-Posttest
Design.
R O X1O
R O X2O
The Control Group would experience the same
history and maturation. Mortality should be the
same because of random assignment. Random
assignment eliminates the selection threat.
However testing and instrumentation could still
be a threat.
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Other Research Designs
Two-Group Treatment-Posttest-Only
Design
R X1 O
R X2 O
There is no pretest so this
eliminates the testing and
instrumentation threat to
internal validly but youdont know about their
knowledge or attitude
coming into the study.
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Other Research Designs
Solomon 4-Group Design
R O X1 O
R X1 O
R O OR O
Note: A blankindicates the
control group,
same as X2
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Quasi-Experimental Designs
Posttest Only Nonequivalent Group
Design
X1 O
X2 O
The absence of R indicates
there is no random
assignment. Sometimes you
will see a dotted line
between the two groups.
This indicates the two
groups may not be
equivalent.
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Quasi-Experimental Designs
Pretest-Posttest Nonequivalent Group
Design
O X1 O
O X2 O
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Time Series Designs
O O O X1 O O O
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External Validity
Can the research be generalized to
other settings?
Population Validity
Personological Variables
Ecological Validity
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Population Validity
Is the sample population similar to the
population the researchers wishes to
generalize to
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Personological Variables
Different people have different
personalities, learning styles, etc., so
the results may not be generalizable to
people who are substantially different
on these personological variables.
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Ecological Validity
The setting or situation in which the
experiment occurred may be differentthan other settings.
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Social Interaction ValidityThreats
Diffusion or Imitation of Treatment
This occurs when a comparison group learnsabout the program either directly or indirectly
from program group participants.
This group may try to imitate or emulate what the
treatment group is getting.
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Social Interaction ValidityThreats
Compensatory Rivalry
The comparison group knows what
the program group is getting and
develops a competitive attitude with
them.
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Social Interaction ValidityThreats
Resentful Demoralization
This is almost the opposite of compensatoryrivalry. Here, students in the comparison
group know what the program group is
getting. But here, instead of developing a
rivalry, they get discouraged or angry andthey give up.
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Social Interaction ValidityThreats
Compensatory Equalization of
Treatment
The researcher is under pressure to
enrich the experiences of the control
group. This pressure may come fromparents, school administrators, etc.
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Ex Post Facto (Causal-Comparative) Research
Explores possible causes and effects
The independent variable is not manipulated,it has already been applied
Focuses first on the effect, then attempts to
determine what caused the observed effect.
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Statistical Analysis
If we are comparing the scores of two
groupsa t-test is normally used. Thevalue of t means nothing by itself
(unlike the value of R). We have to
determine if t is statistically significant
Tea for two
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Statistical Analysis
If we are comparing the scores of three
(or more) groupsAnalysis ofVariance (ANOVA) is used. This testgives us a f value which means nothingby itself. We have to determine if it isstatistically significant.
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Statistical Analysis
If we want to statistically equate two or more
groups (because one group had a high pretestscore) we use Analysis of Covariance
(ANCOVA). This test gives us a f value
which means nothing by itself. We have to
determine if it is statistically significant.
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Changes to look for.
CONVERGENCE-DIVERGENCE
Positive change in the treatment
group without change in the control
group Treatment
Control
Treatment
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Divergence
Positive increments at a different rate
Treatment
Control
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Convergence
The treatment group catches up with the
control group
Control
Treatment
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Cross pattern
The treatment group overpass the control
group Treatment
Control
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TIMEX
No effect
Change in the rate or slope
Change in the intercept
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Questions?