Experimental Method
It may be defined as the study of the relationships among variablesthose manipulated and those measured. It simply enables the
researcher to improve the conditions under which the researcher
observes and thus to arrive at a more precise results. It enables him to
relate a given consequent to a specific antecedent rather than to a
vague conglomeration of antecedents.
It is a scientific method; give more precise, accurate and reliable
results. It is just like an observation under controlled conditions. It acts
on the law of single variable and causing factors. It studies cause and
effect relationship. It is a systematic and logical method for answering
the questions. In this the researcher seeks to evaluate something new.
It leads to contribution to the already acquired fund of knowledge. The
three essential elements in an experiment are; control, manipulation
and observation. In this, experimentor has to imagine that research
conditions are entirely new, they were not existing previously and
recently. It is a method in which we study the effect of d dependent
variable on independent variable. Whatever we know about the
environment, is possible only by observation. All types of experiments
are related with observation and generalization of these observed facts
and it is also possible to test the internal validity.
Definitions
“It is a method of testing hypothesis.”
- Jhoda
“An experiment is an observation under controlled conditioned.” -
F. S. Chapin
“Experimental research is the description and analysis of what will be or
what will occur, under carefully controlled condition.”
- John W. Best
“Experiment is a means of providing the hypothesis whereby the causal
relations between two facts is studied.” -
Green Wood
“The essence of an experiment may be described as observing the effect
on a dependent variable of the manipulation of an independent
variable.”
-
Festinger
Characteristics
(i) Based on the law of single variable.
(ii) This method of research is maximum in use in educational /
social researches where the factors can be controlled.
(iii) Experimental method is a method of testing of clear specific
hypothesis of different intensions.
(iv) It is a bias free estimation of the true effect.
(v) It emphasizes control of conditions and the experimentation of
certain variables in controlled conditions.
(vi) It sets out more or less of the causal type relationship between
the phenomenons.
(vii) It uses standardized tool for experimentation and makes the
evidences very much objective.
(viii) The sample is selected with great precaution and very care is
taken to safe guard extraneous factors.
(ix) This method helps in developing laws, postulate and theories.
(x) It allows for precision and definiteness.
Elements
(1) Control:
The extent to which different factors are accounted for(a) Purposes of Control:
(i) Intervening variables are isolated so that they may effect the dependent variable.
(ii) Not only intervening variables are to be isolated from independent variables but it is also to be ascertained how much it contributed.
(iii) The magnitude is not only ascertained terms of larger or small but also in quantitative terms.
(b) Degree of Control:
It has to be remembered that in social researches high degree of control is not possible as in laboratory situation.
(c) Methods of Control:
The researcher directs efforts towards controlling the variables which are related to the independent variable otherwise it will be difficult to ascertain which is responsible for effect on dependent variable. The following methods are used for controlling;
(i) Random assignment of subjects to groups:
It means that subjects are assigned in such a way that every member has an equal opportunity of being chosen.
(ii) Matching subjects with random assignment:
The subjects are assigned to groups to match individual’s subjects on as many extraneous variable as the researcher can identify. They may be;
(a) Subject to subject matching,
(b) matching for mean and standard deviation,
(c)Ranking of subjects on matching variable.
(iii) Random assignment on the basis of homogeneous selection:
It is done to make groups comparable on an extraneous variable so as to select groups those are as homogenous as possible on the variable. The variable may be like socio-economic –status and sex etc.
(iv)Techniques of analysis of Co-variance:
It is attempted to control the variation within the groups .A co-variate is a variable which the researcher has not been able to control.
(v) Methods of using subjects as their own controls:
It is done to assign the same subjects to two experimental treatments and then to obtain measurements of the subjects under one treatment and then on the other. But there is practical difficulty in this method in some cases
(2) Manipulation
In the experimental method manipulation is done to set the stage for the occurrence of the factor whose performance is to be studied under conditions in which all other factors are controlled. Variables which can be manipulated may be personality characteristics, attitudes, teaching methods, type of motivation etc.
(3) Observation
Another element of the experimental method is that the effect of the manipulation of independent variable on the dependent variable is studied or observed. The technique of observation is applied if measurement is not possible.
(4) Replication
In spite of attempts of controlling extraneous variables, some extraneous variable and some discrepancies remain and influence the results. Thus replication is a matter of conducting a number of subexperiments within the frame work of an overall experiment design.Features
(i) It is based on law of the single variable. It means if one element
is added or subtracted in one of the two situations and other
situation is kept as it is, the change in the two situations is the
result of that single variable.
(ii) It is applicable when significant factor or conditions can be
controlled.
(iii) It is not a perfectly precise method in educational research as in
scientific method.
(iv) Control group and experimental group are never identical as they
should be for an exact experiment.
Experimental Validity
Two types of validity are involved;
(i) Internal Validity:
It is the minimum without which an experiment is useless. The crucial
point is whether the independent variable created the effect on the
dependent variable. It means that some uncontrolled extraneous
factors do not affect the dependent variable. The following eight
extraneous factors are to be controlled for obtaining internal validity;
a) Contemporary confounding factor.
b) Maturation of the subject with the passage of time,
c) Experience in pre-test reflecting itself in the post test,
d) Change in the calibration of the measuring instruments,
e) Tendency for extreme scores to regress towards the mean,
f) Difference in the selection of subject in the pre-test and posttest,
g) Differential loss of subjects from the experimental and control
groups tend to bias the results of the experiment,
h) Interaction of selection and maturation and selection and
history.
(ii) External Validity:
The crucial point is what is the applicability of the findings beyond the limits of particular experiment. Are the results valid in general for students? The following factors are to be controlled for obtaining external validity;
a) Selections of sample with some special characteristics make the application restrictive.
b) Pre-testing may sensitize the subject to the experimental factor.
c) Effects of experimental procedures restrict the generalize ability of the findings.
d) Effects of a treatment on a subject previously exposed to other treatments cannot be generalized to other subjects who have not undergone the same sequence of treatments.
Types of Experimental Designs
It is to the researcher what a blue –print is to an architect. The following
are the factors upon which the selection of designs depends;
(i) What is the nature of the experiment?
(ii) What is the main purpose of the experiment?
(iii) What types of the variables are to be manipulated?
(iv) What is the nature of data?
(v) What is the competence level of the experimentor?
The experimental designs are classified as follows;
(a) Pre-experimental designs
In this type of design there is no control over extraneous or situation
variables. They are divided into the following categories;
One Group, Pre-test –Post-test Design
| Pre-Test | Independent Variable | Post-Test |
| T1 | X | T2 |
Since there is no control group in this research design it cannot be checked whether the obtained result is due to treatment or extraneous variables.
Two Group, Static Design
| Group | Independent Variable | Post-Test |
| Experimental | T2 | |
| Control | T2 |
In this design, the two groups are assigned but neither on the basis of randomization nor matching. There is no pre-test so the researcher cannot measure the difference on account of treatment. In this design, comparison is made on the basis of post-test, in experimental group and control group.
(b)True-experimental designs
In these designs, the researcher attempts to control the effects of
history, maturation, testing, measuring instruments etc.
Two groups, Randomized Subject, Post –test only Design
| Randomly assigned Group | Independent Variable | Post-Test |
| Experimental | T2 | |
| Control | T2 |
In this design, there is provision of randomization of subjects to the two groups, it assures the equivalence of groups and since there is no provision of pre-test there is probability of interaction effect. However, the use of the designs restricts the external validity of the experiment. There are some situations which do not permit selection of subjects at random.
Two groups, Randomized Matched Subjects, Post-test only Design
| Randomly assigned group after matching | Independent Variable | Post-Test |
| Experimental | T2 | |
| Control | T2 |
This design is the most useful where small groups are to be used. In this
design the subjects are randomly assigned to two groups after
matching, it ensures strengths to design.
But it is very difficult to match the subjects with precision
because it reduces the sizes of the sample. In some cases it is not
possible to match one or more potential subjects. If some subjects are
to be reduced for this purpose, a bias is introduced in the sample.
Randomized groups—Pre-test, Post-test Design
| Randomly assigned | Pre-Test | Independent Variable | Post-Test |
| Experimental Group | T1, E | T2, E | |
| Control Group | T1, C | T2, C |
In this design additional check is provided for the equality of
Experimental group and control group because there is provision of pretest. The nature of the design is such that it controls most of the
extraneous variables.
However, the design has certain limitations. Firstly interaction
between pre-test and treatment may sensitize subjects which may
affect the results. Secondly, interaction of experimental variable with
other factor limits its generalization. Thirdly, experimental procedure
may affect normalcy.
The Randomized Solomon Three Group Design
| Randomly assigned | Pre-Test | Independent Variable | Post-Test |
| Experimental Group (E) | T1, E | T2, E | |
| Control Group (C1) | T1, C1 | T2, C1 | |
| Control Group (C2) | No Pre-Test | T2, C2 |
In this design check is provided for the equality of Experimental group and control group because there is provision of pre-test. The nature of the design is such that it controls most of the extraneous variables. The provision of the second control group ensures control interaction effect of Pre-test and treatment.
The Randomized Solomon Four Group Design
| Randomly assigned | Pre-Test | Independent Variable | Post-Test |
| Experimental Group (E) | T1, E | T2, E | |
| Control Group (C1) | T1, C1 | T2, C1 | |
| Control Group (C2) | No Pre-Test | T2, C2 | |
| Control Group (C3) | No Pre-Test | T2, C3 |
In this stage check is provided for equality of Experimental group and
control group, because there is provision of pre-test. The nature of the
design is such that it controls most of the extraneous variables. The
provision of the second control ensures control interaction effect of pretest and treatment. The design controls any possible contemporary
effects between pre-test and post-test. The result in this design
provides greater confidence.
However this design is such that it is difficult to conduct in
practical situation. There is a difficulty of statistical application in this
design.
(C) Factorial Design
This design enables the experimenter to evaluate or manipulate two or
more experimenter to evaluate or manipulate two or more variables
simultaneously in order to study the effects of number of independent
factors singly as well as the effects due to interactions with one another.
Single Factorial Design of 2 2
There are two independent variables and each of the independent
variables has two values. The first independent variable which is
manipulated and has two values is called the experimental variable. The
second independent variable which is divided into levels may be called
control variable.
In this design the impact of more than one variable can be studied
simultaneously. In this not only the significance of difference of
different levels is studied but interaction effect can also be studied.
However, if too many variables and two many levels are studied, the
experiment and statistical analysis becomes too difficult to manage.
Steps of Experimental Research Methods
The procedures of the experimental method are to be executed under
the following steps;
(i) Identifying, defining and delimiting the problem:
The problem that can be verified or refuted by the experimental data
should be selected first. The variables to be investigated are defined in
operational terms.
(ii) Reviewing the literature:
After selecting the problem, the related literature and experiments
should be reviewed and the method of approach or experimental design
to be pursued should be planned or outlined.
(iii) Formulating the hypothesis and deducing their consequences:
The problem has to be converted into a hypothesis that can be verified
or refuted by experimental method.
(iv) Drawing up the experimental design:
This section should place primary emphasis on the question of control,
randomization, replication, place of the experiment, duration of the
experiment, selecting or constructing and validating instruments to
measure the outcomes of the experiment and conducting pilot for trial
run tests to perfect instrument.
(v) Defining the population:
It is necessary to define the population precisely so that there can be no
question about population to which the conclusions are to apply. It may
consist of selecting a sample of subjects to represent a given population
and pairing of subjects to secure homogeneity.
(vi) Administration of test / Carrying out the study:
It is necessary to insist on close adherence to plans and experimental
design. This will involve controlling variable or non-experimental
factors, applying the experimental factors and keeping the careful
record of steps in the procedure.
(vii) Measuring the outcomes / Collection of Data:
Careful consideration must be given to the selection of the criterion on
the basis of which the results are measured.
(viii) Analyzing and interpreting the outcomes:
The result pertaining to the factors under study should be clearly noted.
The analysis of data demands expert use of statistical procedures. Only
then the analysis becomes the basis for valid interpretation.
(ix) Drawing the conclusions:
The conclusions of the study must be restricted to the population
actually covered; care must be taken not to over ganaralize the results.
The result also pertains to the conditions under which they were
derived. Care must be taken to restrict the conclusions to the conditions
actually present in the experiment.
(x) Reporting the results:
The study must be reported in sufficient details.
Continue to Index