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QUASI EXPERIMENTAL RESEARCH DESIGN

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Andrea Higuera Lagos

on 22 February 2014

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Transcript of QUASI EXPERIMENTAL RESEARCH DESIGN

QUASI EXPERIMENTAL RESEARCH DESIGN
Experimental Research
1. Most of them take place in labs.

2. They assign the participants randomly.

3. It is demanding and it has to fulfill all
the requirments of a strong-experimental
research.

4. Manipulates the variables.
Quasi- Experimental
1. They used to develop in natural context.
In education ( classrooms).

2. It doesn´t assign participants randomly,
they have a single intact group.

3. It´s flexible.

4. It Doesn´t provide for full control of
variables.
Conclusion
Quasi expermiental Research designs are used when not all the demands of experimental research can be met.
Quasi - Experimental Research
It is an experimental research that doesn´t provide for full control of variables.

PURPOSE:
It estimates the impact of an intervention and test de research question.

WHEN

* When random assignment cannot be used.
* When you have a single intact group.



Requirements of a Regression - Discontinuity Design.
EXAMPLE
NON-EQUIVALENT COMPARISON GROUP.

It consists in giving a control and experimental group a pre-test and a posttest after the treatment.

CONTROL GROUP








EXPERIMENTAL GROUP


The responses of the two groups are analized in one of the two ways. First comparing the pre-test and posttest differences or comparing the control and experimental group´s posttest scores using analysis of covariance. ( ANCOVA)







PRE-TEST

POSTTEST
PRE-TEST
POSTTEST




PRE-TEST

POSTTEST
PRE-TEST



PRE-ASSIGNMENT
MEASURE

REGRESSION DISCONTINUITY DESIGN

A dessign that validater the effect of a treatment condition by looking for a descontinuity in regression lines between individuals who score lower and higer than some predetermined cutoff score.













The outcomes of the Pre-assignment measure are divided, those who where above the cutoff score: ( take treatment) and those who where below score : ( Control group).
Finally you compare the outcomes to determine if the treatment was effective.


POSTTEST
MEASURE
PRE-ASSIGNMENT
MEASURE
POSTTEST
MEASURE
INTERRUPTED TIME DESIGN

When we only have one group of participants available, and NO CONTROL GROUP, there are many confounding variables, so ..to control then, we must think of mechanisms other than the use of a control group. That is the INTERRUMPTED TIME DESIGN.

NO CONTROL GROUP
.













EXPERIMENTAL GROUP

A single group of participants is pretested a number times (baseline) , then they are exposed to a teatment condition and then posttested a number of times during the treatment.





Example:


All the students attended an experimental
classroom for at least one period each
school day, so there was a single intact
group of participants available for
experimentation, wich meant that some
form of a time series design had
to be used.

EXPERIMENTAL GROUP
CONTROL GROUP
cuttoff score
Cuttoff score
Assigned must be based
on the cutoff score.
It must be an ordinal variable
Relationship between
variables must be known
to avoid a biased.
All the participants
must be of the same population.
Assignment must be
under control of the
experimenter to avoid
bias.
you must be alert for the influence of
extraneous variables that can counfound
results.

1. A researcher wants to prove the efficacy of a reading program (XXXX) to improve the reading comprehension.

2. He select two groups (CONTROL - EXPERIMENTAL) the control group is going to continue with the traditional reading process and the experimental is going to take the new reading program.

3. Then you will take a PRE-TEST and a POSTTEST after applying the treatment to the experimental group.

4. As they were different groups and not random selection could be biases, so you use analysis technics to correct them. (It is the ANCOVA) to avoid possible biases.







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