Concept of Variance, Partitioning of variance, Source of error variance. Control techniques

 Concept of Variance, Partitioning of variance, Source of error variance. Control techniques

Research in common parlance referred to as search for knowledge. It can also be defined as a scientific and systematic search for pertinent information on a specific topic. In fact, research is an art of scientific information. Redman and Mory defines research as a “systematized effort to gain new knowledge.”Some people consider research as a movement from the known to the unknown. According to Clifford Woody research comprises defining and redefining problems, formulating hypothesis or suggesting solution; collecting, organizing and evaluating data; making deductions and reaching conclusions; and at last carefully testing the conclusion to determine whether they fit the formulating hypothesis. Research is, thus, an original contribution to the existing stock of knowledge making for its advancement. It is the persuit of truth with the help of study, observation, comparison and experiment. In short, the search for knowledge through objective and systematic method of finding solution to a problem is research. As such the term ‘research’ refers to the systematic method consisting of enunciating the problem, formulating a hypothesis, collecting the facts or data, analyzing the facts and reaching certain conclusions either in the form of solutions(s) towards the concerned problem or in certain generalizations for some theoretical formulation.

The purpose of research is to discover answers to questions through the application of scientific procedures. The main aim of research is to find out the truth which is hidden and which has not been discovered as yet.

Every science has goals. In physics, the goals are concerned with learning how the

physical world works. In astronomy, the goals are to chart the universe and understand both

how it came to be and what it is becoming.

 The goals of psychologist conducting basic research are to describe, explain, predict

and control behavior.

 Description: What is Happening?

 Explanation: Why is it Happening?

 Prediction: When Will it Happen Again?

 Control: How can it be Changed?

RESEARCH DESIGN

MEANING OF RESEARCH DESIGN

Research design is the plan, structure and strategy of investigation conceived so as to obtain answers to research questions and to control variance. The plan is the overall scheme or the program of the research. It includes an outline of what the investigator will do from writing the hypothesis and their operational implications to the final analysis of data. Structure of the research is outline of the research design, and the scheme is the paradigm of operation of the variable. Strategy includes the methods to be used to gather and analyze the data. In other words, strategy implies how the research objective will be reached and how the problems encountered in the research will be tackled. (Kerlinger, 2007)

 A traditional research design is a blueprint or detailed plan as to how a research study is to be completed. That is, how it would operationalise variables so that they can be measured, how to select a sample of interest to the research topic, how to collect data to be used as a basis for testing hypothesis, and how to analyze the results. (Thyer, 1993)

FUNCTION OF A RESEARCH DESIGN

The function of a research design is:

 To provide answer to research question and 

 To enable the researcher to answer question as validly, accurately and as economically as possible.

CONCEPT OF VARIANCE

Variance is a measure of the dispersion or spread of a set of scores. It describes the extent to which the scores differ from each other. Variance and variation, though used by synonymously, are not identical terms. Variation is a more general term which includes variance as one of the statistical methods of representing methods. The main technical function of research design is to control variance. Research design is a set of instructions to the investigator together analyze data in certain ways. Therefore, research design acts as control mechanism and enables the researcher to control unwanted variances. Variance control is a central theme of research design.

PARTITIONING OF VARIANCE

The researcher is directly concerned with three types of variance namely experimental variance, extraneous variance and error variance. Main functions of research design are to maximize the effect of systematic variance, control extraneous variance and minimize error variance. A discussion of these variances is presented below.

SYSTEMATIC VARIANCE: By constructing an efficient research design the investigator attempts to maximize the variance of the variable of substantive research hypotheses. Systematic variance is the variability in the dependent measure due to the manipulation of the experimental variable by the experimenter. An important task of the experimenter is to maximize this variance. This objective is achieved by making the level of the experimental variable as unlike as possible. Suppose an experimenter is interested in studying the effect of intensity of light on visual acuity. The experimenter decides to study the effect by manipulating three levels of light intensity, i.e. 10ml, 15ml, 20ml. as the differences between any two levels of the experimental variable is not substantial, and there is little chance of separating its effect from the total variance. Thus, in order to maximize systematic variances, it is desirable to make the experimental conditions (levels) as different as possible. In this experiment it would be appropriate, then to modify the levels of light intensity to 10ml, 20ml, 30ml so that the difference between any two levels is substantial.

EXTRANEOUS VARIANCE

Extraneous variance is produced by the extraneous variables or the relevant variables. An experimenter always tries to control the relevant variables and thus, also wants to eliminate the variances produced by these variables. For elimination of extraneous variance it is essential that the extraneous variables be properly controlled. There are four ways to control the extraneous variances.

1. Randomization: It is considered to be the most effective way to control the variability due to all possible extraneous sources. It is a procedure for equating groups with respect to secondary variable. Randomization means random selection of the experimental units from the larger population. Random assignment means that every experimental unit has an equal chance of being placed in any of the treatment conditions or group. In using randomization method some problems may be encountered. It is possible to select a random sample from a population, but then assignment of experimental units to groups may get biased. Random assignment of subjects is critical to internal validity. If subjects are not assigned randomly, confounding may occur.

 Randomized group design and randomized block design are the examples of research design in which randomization is used to control the extraneous variable.

2. Elimination: this procedure is the easiest way to controlling the unwanted extraneous variable through elimination of variable. Suppose, the sex of the subject as unwanted secondary variable, is found to influence the variable in an experiment. Therefore the variable of sex has to be controlled. The researcher may decide to take either all males and all females in an experiment and thus, controlled through elimination the variability due to the sex variable.

 By using elimination for controlling the extraneous variables, researcher looses the power of generalization. If the researcher selects the subject from a restricted range then the researcher can generalize the results within restricted range and not outside it. Elimination procedure is used in non-experimental design.

3. Matching: is also a non experimental design procedure, is used to control the extraneous source of variance. In case of controlling organismic and background variable matching is used in this procedure, the relevant variable are equated or held constant across all conditions of experiments. Suppose if the researcher finds that the variable of intelligence is highly correlated with the dependent variable, it is better to control the variance through matching on the variable of intelligence. However as amethod of control matching limits the availability of subjects. If the researcher decides to match subjects on two or three variables he may not find enough subjects for the experiment. Besides this the method of matching biases the principles of randomization.

4. Statistical Control: in this approach, no attempt is made to restrain the influence of

secondary variables. In this technique, one or more concomitant secondary variables (covariates) are measured and the dependent variable is statistically adjusted to remove the effect of the uncontrolled sources of variation. Analysis of covariances is one such technique. It is used to remove statistically the possible amount of variation in the concomitant secondary variable.

ERROR VARIANCE

The third function of a research design is to minimize the error variance. The error variance is defined as those variance or viabilities in the measures, which occurs as a function of the factors not controllable by the experimenter. Such factors may be related to the individual differences among the subjects themselves such as to their attitude, motivation, need, ability etc. They may be related to what is commonly called the errors of measurements such as the differences in trials, differences in conditions of experiment, temporary emotional state of the subject, fatigability etc.

 Statistical control can be applied to minimize such error variance. For example, repeated measures design can be used to minimize the experimental error. By this technique the variability due to the individual differences is taken out from the total variability, and thus, the error variance is reduced. Analysis of covariance is also a technique to reduce the error variance. Further, error variance can be controlled by increasing the reliability of measurement by giving clear and unambiguously instructions and by using a reliable measuring instrument etc.

SOURCES OF ERROR VARIANCE

 Poorly designed measurement instruments ( instrumental error)

 Error emanating from study subjects ( e.g., response error)

 Contextual factors that reduce a sound/ accurate measurement instrument’s capacity to measure accurately

 

CONTROL TECHNIQUES

Controlling variance of confounding variables:

 It can produce undesirable variation in the study’s dependent variables, and cause misleading or weird results

 In Experimental Settings :

1. Conducting the experiment in a controlled environment ( e.g., laboratory), where we can hold values of potential confounding variables constant

2. Subject selection (e.g., matching subjects in experiments)

3. Random assignments of subjects ( variation of confounding variables are evenly distributed between the experimental and control group)

 In Survey Research:

1. Sample selection (e.g., including only subjects with appropriate characteristics – using male college graduates as subjects will control for potential confounding effects of gender and education)

2. Statistical Control

CONCLUSION

There are several research designs and the researcher must decide in advance of collection and analysis of data as to which design would prove to be more appropriate for his research project.

An Effective research design is a function of - 

1) Adequate variability in values of research variables 

2) Precise and accurate measurement 

3) Identifying and controlling the effects of confounding variables and 

4) Appropriate subject selection

REFERENCE

1. Kerlinger, F N (1986). Foundations of Behavioural Research. New York: Holt Rinehart and Winston.

2. Thyer, B.A. (1993) ‘ Single-systems Research Design’ in R.M. Grinnell (ed), Social Work, Research and Evaluation ( 4th ed), Itasca Illionois:Peacock

3. Kothari, C.R. (2004). Research Methodology: Methods and Techniques. New Delhi: New Age International Publishers.