What do you mean by research design? Discuss the basic purposes of research design. How can you minimize the extraneous variance? Discuss the various ways to control the extraneous variable.

Research design refers to the overall strategy that you choose to integrate the different components of the study in a coherent and logical way, thereby, ensuring you will effectively address the research problem constitutes the blueprint for the collection, measurement and analysis of data. Research design defines the study type, research questions, hypotheses, variables and data collection methods. It is a plan, structure and strategy of investigation so conceived so as to obtain answers to research questions or problems.

The purposes of research design are:

1. To provide answers to research questions.
2. To control variance under study.
3. To maximize variance of variable.
4. To control extraneous variable.
5. To minimize error variance.

We can minimize the extraneous variance by two methods:

• The reduction of errors of measurement through controlled conditions.
• An increase in the reliability of measures.

We can control the extraneous variance which is one of several descriptors of a probability distribution. In particular, the variance is one of the moments of a distribution. In that context, it forms part of a systematic approach to distinguishing between probability distributions, While other such approaches have been developed, those based on moments are advantageous in terms of mathematical and computational simplicity.