Generally a good research design minimizes bias and maximizes the reliability of the data collected and analyzed. The design which gives the smallest experimental error is reported to be the best design in scientific investigation. Similarly, a design which yields maximum information and provides a opportunity for considering different aspects of a problem is considered to be the most appropriate efficient design . Thus the question of a good design is related to the purpose or objective of the research problem and also with the nature of the problem to be studied. A good research design should satisfy the following four conditions namely objectivity, reliability, validity and generalization of the findings.
1. Objectivity: It refers to the findings related to the method of data collection and scoring of the responses. The research design should permit the measuring instrument which are fairly objective in which every observer or judge scoring the performance must precisely give the same report. In other words, the objectivity of the procedure may be judged by the degree of agreement between the final scores assigned to different individuals by more than one independent observer. This ensures the objectivity of the collected data which shall be capable of analysis and drawing generalizations.
2. Reliability: Reliability refers to consistency through out a series of measurements. For eg: if a respondent gives out a response to a particular item, he is expected to give the same response to that item even if he is asked repeatedly. If he is changing his response to the same item, the consistency will be lost. So the researcher should frame the items in a questionnaire in such a way that it provides consistency or reliability.
3. Validity: Any measuring device or instrument is said to be valid when it measures what it is expected to measure. For eg: an intelligence test concucted for measuring the I.Q should measure only the intelligence and nothing else, and the questionnaire shall be framed accordingly.
4. Generalizability: It means how best the data collected from the samples can be utilized for drawing certain generalisations applicable to a large group from which sample is drawn. Thus a research design helps an investigator to generalize his findings provided he has taken due care in defining the population, selecting the sample, deriving appropriate statistical analysis etc. while preparing the research design. Thus a good research design is one which is methodologically prepared and should ensure that:
a) The measuring instrument can yield objective, reliable and valid data.
b) The population is clearly defined.
c) Most appropriate techniques of sample selection is used to form an appropriate sample.
d) Appropriate statical analysis has been carried out, and
e) The findings of the study is capable of generalisations.