Quantitative Research (Part 1)
Experimental Research
The uniqueness
1. purposely conducted to influence a specific variable
2. able to test the hypotheses of a research on cause-and-effect relationships.
Essential characteristics
1.Comparison of groups
>Consist of;
>Experimental group – with treatment
>Control group – without treatment or
>Comparison group – with different treatment
>The comparison ensures whether the treatment is effective or not.
2.Manipulation of the independent variable
>The researcher determines the treatment and which group will be the experimental group.
>The independent variable is tested in a number of ways;
>One variable vs another
>Presence vs absence of treatment
>Varying degrees of the same treatment
3.Randomization
>It features;
>Random assignment:
every sample has an equal opportunity of being assigned to either experimental or control group.
>Random selection:
every member of the population has an equal opportunity of being assigned to be a member of the sample.
>Three essential notes
>This is conducted before the experiment starts.
>This is a process of assigning individuals to groups.
>This enables groups that are equivalent to be formed by the researcher.
>Random assignment is meant to discard extraneous variables.
Control of Extraneous Variables
1.This is crucial as to discard/minimize the effect of extraneous variables.
2.Some of the suggested ways;
>Randomization
>Holding certain variables constant
>Building the variable into the design
>Matching
>Using subjects as their own controls
>Using analysis of covariance
Group Designs in Experimental Research
Considerable as Poor or Weak Experimental Designs;
1.The One-Shot Case Study
>no comparison = no control
2The One-Group Pretest-Posttest Design
>No comparison=the researcher would not know whether the result is due to the treatment or not
3.The Static-Group Comparison Design
>Also known as nonequivalent control group design
>Static means two existing groups are used. Therefore, it is not a random assignment.
>This may lead to extraneous variable = differential subject characteristics
4.The Static-Group Pretest-Posttest Design
>Pretest is given to both groups.
>Posttest–Pretest = Gain/Change
>Gain/change=improve (depends on the cases)
True Experimental Designs
1.The Randomized Posttest-Only Control Group Design
>features independent variable and control groups that are formed by random assignment
>the presence of control=good
>the presence of threats: mortality
2.The Randomized Pretest-posttest Control Group Design
>the presence of pretest
> features independent variable and control groups that are being tested twice (pretest and posttest)
>pretest may lead to pretest treatment interaction threat
3.The Randomized Solomon Four-Group Design
>to discard the possible effect of pretest
>features 4 groups;
a.2 groups with pretest
b.2 groups without pretest
>enables the best control of the threats
>drawbacks;
a.requires large sample
b.requires more energy and effort
4. Random Assignment with Matching
>pairs of individuals could possibly be matched on certain variables
>this could be done in two ways:
a.Mechanical Matching
>a process of pairing two individuals with similar scores on a specific variables
>it is difficult as it requires a large sample and there are samples that will be taken out from the research as they could not be paired with anyone.
b.Statistical Matching
>each sample is given predicted scores
>the predicted scores will be compared with the actual scores
>the difference is then used to pair the samples
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