1) Define experimental method. Explain what do you understand by a variable
Experimental method is central to scientific method or positivist approach to discovery of knowledge. It is to study cause-effect relation between two entities (called variables) by direct observation and measurement under controlled conditions generally in a laboratory. It can also be carried out outside the laboratory also.

2) What is hypothesis? Describe null hypothesis.
A hypothesis is a formal affirmative statement predicting a single research outcome, a tentative explanation of the relationship between two or more variables. Null hypothesis states a relationship between two variables where there is no significant difference between the experimental and control groups.

3) Define validity. What are its different types?
Literally it refers to logical soundness and consequent acceptability of an entity or research results. In experimental research it is of two types viz. internal and external validity. It refers to the accuracy of observation and measurement of the dependent variable only under the impact of independent variable. Internal validity is high when all the confounding variables are identified and kept under control. Laboratory research is high in internal validity as the independent variables can be controlled
effectively while changes in the dependent variable can be measured minutely; and intervening variables can be kept under check. It refers to use generalisability of the results i.e. the degree of their universality. Laboratory experiments are low in external validity whereas field experiments are high in external validity.

4) Enumerate the limitations of experimental method.
Limitations of experimental method are in creating a control group. This is particularly true of social sciences where the population is human beings. Other limitation lies in validity of the observations in social sciences as human beings may not be observed exactly

Keywords:
Control Group : Group/population/subjects not exposed to any treatment. It also forms independent variable.
Experimental Group : Group of population/subjects exposed to treatment and observation to measure the change. It is dependent variable.
Empirical Knowledge : Knowledge based on objective observation and experience as contrasted from intuitive or authority centered knowledge.
Hypothesis : A statement, based on an informed guess, predicting relations between two or more variables. Every experimental research starts with a hypothesis to prove or disprove it.
Randomisation : It is a statistical process of sample formation to ensure natural and representative membership in a sample of the whole population. Generalization of results depends much upon the randomization.
Sample : A representative population under study formed in case the field of research is too vast to be studied wholly.
Validity : A measure of accuracy of results and their generalization to other situations.Source:

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