One Factor at a Time vs Designed Experiments

One Factor at a Time (OFAT) and Designed Experiments are two distinct methodologies applied in the field of experimental design and scientific investigations. They each hold unique applications and implications, especially in the context of school science.

OFAT, as indicated by its name, involves changing one factor or variable at a time, while maintaining all other variables constant. The simplicity and intuitiveness of this method make it a popular choice for school science projects where constraints in terms of resources and time may exist (Zuur et al., 2009). For instance, a student examining the impact of light exposure on plant growth might alter the duration of sunlight exposure each plant receives while keeping other variables such as water and soil type constant. OFAT is useful for demonstrating the fundamental concept of variables and the potential outcome of changing one. However, it fails to account for potential interactions between variables, which is a common occurrence in real-world phenomena.

Designed experiments, on the other hand, also known as factorial design or Design of Experiments (DoE), manipulates several factors at once, aiming to observe the effects of each factor and, crucially, the interactions between them (Anderson & Whitcomb, 2016). Using the previous example, a designed experiment could modify both the amount of sunlight and water at the same time, allowing detection of any potential interaction effects. For instance, less water might be necessary if a plant is receiving less sunlight. Designed experiments, while more complex in design and analysis, offer a more accurate and comprehensive understanding of the system under investigation.

Both OFAT and designed experiments follow a systematic approach, and both are rooted in the scientific method – the processes of observing, hypothesizing, experimenting, analysing, and concluding. They each offer paths to knowledge generation or theory confirmation, a shared goal of scientific exploration.

In school science, OFAT is often introduced first as it aligns well with basic understandings of the scientific method and variable manipulation. As learners progress, designed experiments can be introduced, preparing students for higher-level scientific inquiry and providing a more sophisticated toolset for scientific investigations. Understanding both methodologies, along with their strengths and limitations, equips students with a comprehensive understanding of scientific enquiry.

Despite their differences, the most important shared attribute between OFAT and designed experiments is their grounding in the scientific method and their capacity to foster scientific thinking. Regardless of the experimental design chosen, students learn to formulate hypotheses, conduct experiments, and interpret results. They understand that experimentation is a cornerstone of science and that our current body of knowledge is the result of careful, systematic investigations.

**References:**

- Anderson, M. J., & Whitcomb, P. J. (2016). DOE simplified: practical tools for effective experimentation. CRC Press. [Link](https://www.routledge.com/DOE-Simplified-Practical-Tools-for-Effective-Experimentation-Third-Edition/Anderson-Whitcomb/p/book/9781498746490)

- Zuur, A. F., Ieno, E. N., & Elphick, C. S. (2009). A protocol for data exploration to avoid common statistical problems. Methods in Ecology and Evolution, 1(1), 3-14. [Link](https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2009.00001.x)