Usually how an experiment goes is having IVs and DVs as well as some extraneous variables that are not practically possible to control. In correlation, these are called the two determined variables. Experiments look for changes and variations in the DV between two or more than two, levels of the IV which are put down by the experimenter/researcher.

The essential aspect is for the IV to be concretely defined or better, operationalized so that the manipulation of the conditions, project the intended effects.

To make it clear:

Variables are factors that are prone to change or can be changed and moulded. 

Operationalizing: Involves defining each variable of interest in terms of the operationalization in terms of the operations taken to ‘measure’ it.  This allows vague components to be empirically measured and observed. 

In order to be surer about their research’s findings, variables need to be controlled. Specifically, in experiments where extraneous variables are likely to disrupt and complicate the results and distorting them for interpretation. 

Confounding Variables, can either work against the reaction of the IV or in favour by increasing the intended/expected outcome of the IV because they selectively act on DVs. Thus, they serve as a “consequential effect” of the IV and you are left with no chance of knowing what caused the change. 

Extraneous Variables which randomly effect all levels of the IV aren’t so problematic. The difficult part is to identify and select which variables to manage before the experiment launches. It is however. Also, important to note how if extraneous variables are not recognized and acknowledged beforehand, they become uncontrollable variables, which would make the results difficult to be construed as it would be difficult to distinguish the reactions/effects of the IV from those of other variables that effect the DV.  

There are controls present that ensure that IVs represent what they are designed to I.e the differences between them will produce the intended scenarios to examine the hypothesis – ensuring validity and reliability.  This enables every participant in the study to be treated equally so that no participant variable arises. This is called standardization. 

This is achieved by having a unified, standardized set of instructions, that provide the same instructions to every participant involved in the study. For instance, a 10-question questionnaire which asks about people’s dietary habits – all the participants should be told how to answer it only strictly regarding their food patterns, so if any social desirability is there, it should be equal. 

Procedures also need to be strictly standardized - this involves having equipment, tests and designs that are consistent, measuring the same variable every time and always do so in the exact, identical way. Assess the questionnaire about people’s dietary habits again. They should again focus on strictly people’s food consumption patterns rather than why food patterns are like that. It is related but not necessary to the context. 

In laboratory experiments, standardization is easier because variables such as equipment are better and more easily controlled.  An example of this would be the stopwatch which is used to regulate time intervals in the experiment or FMRI Brain scans which is an objective measure. They do however also have to be performed in a standardized manner for them to be interpreted. The controls used should be appropriated and be taught how to implement.