What are the best ways to control variables in experimental design?

1 Define the variables

The first step in controlling variables is to define them clearly and consistently. Variables are the factors that can affect the outcome of an experiment, and they can be classified into three types: independent, dependent, and controlled. Independent variables are the ones that you manipulate or change intentionally, such as the dosage of a drug or the temperature of a culture. Dependent variables are the ones that you measure or observe as a response to the independent variables, such as the growth rate of a cell or the expression level of a gene. Controlled variables are the ones that you keep constant or minimize their variation throughout the experiment, such as the pH of a solution or the source of a sample. By defining the variables, you can establish a clear relationship between the cause and the effect, and avoid confusion and ambiguity.

2 Choose an appropriate design

The second step in controlling variables is to choose an appropriate design for your experiment. The design refers to the structure and layout of your experiment, such as how many groups, treatments, replicates, and measurements you will use. The design should be aligned with your research question, hypothesis, and objectives, and it should also consider the availability and feasibility of your resources and methods. Some common types of experimental designs in biotechnology are randomized, factorial, split-plot, and crossover designs. Each design has its own advantages and disadvantages, depending on the nature and complexity of your experiment. By choosing an appropriate design, you can optimize the use of your variables, reduce the sources of error and bias, and increase the power and sensitivity of your analysis.

3 Implement standard procedures

The third step in controlling variables is to implement standard procedures for your experiment. Standard procedures are the rules and guidelines that you follow to perform your experiment consistently and accurately, such as how to prepare, handle, store, and dispose of your materials and equipment, how to calibrate, operate, and maintain your instruments and devices, how to collect, record, and store your data and information, and how to analyze, interpret, and report your results and findings. Standard procedures can be based on existing protocols, manuals, or best practices, or they can be developed and adapted for your specific experiment. By implementing standard procedures, you can ensure the quality and integrity of your experiment, minimize the variation and uncertainty of your variables, and facilitate the replication and verification of your results.

6 Review and refine the experiment

The sixth step in controlling variables is to review and refine your experiment based on your feedback and findings. Reviewing means reflecting and commenting on your experiment, such as what worked well, what did not work well, what can be improved, and what can be learned. Refining means modifying and improving your experiment, such as repeating, replicating, extending, or revising. Reviewing and refining can help you enhance and optimize your experiment, and address any limitations or gaps that may exist in your design, procedures, or analysis. By reviewing and refining your experiment, you can increase the reproducibility and generalizability of your results, and generate new insights and hypotheses for your variables.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?