Experimental Design and Communicating Scientific Findings Tyler Bassett and Tomomi Suwa

Designing A Scientific Study Thoughts on Experimental Design

Two types of studies 1) Observational 2) Experimental

Observational Study -Observe subjects and measure variables of interest without directly assigning treatments to the subjects Reasons for Observational Study: -Less powerful – correlation does not imply causation - Experiment would violate ethical standards: human disease - Experiment is logistically impossible/impractical: rare species, stars, river

Manipulative Experiment Vary one factor explicitly and keep other factors constant “Cleaner” than observational study, easier to identify causative agent When one thinks of “science,” this is what they are thinking of!

Elements of Experimental Design Independent vs. Dependent variable Control Replication Randomization

Independent vs. Dependent variable Independent Variable – something that is intentionally changed or manipulated by the scientist Dependent Variable – something that might be affected by the change in the independent variable – What is observed and measured

How do elevated soil nutrients affect plant growth ? Effect of on independent var.dependent var. What is an independent and dependent variable? NO 3 - NH 4 + PO 3 - Also referred to as predictor and response variables

Control The control and experimental groups must be identical in every way except for the introduction of a suspected causal agent into the experimental group (s). Compare to an experimental group in a test of a causal hypothesis – often to demonstrate how much the causal agent changes the dependent variable

How do elevated soil nutrients affect plant growth ? What is the control here? What does it mean? Add NAdd PAdd N,PControl NO 3 - NH 4 + PO 3 -

Replication Repetition of an experiment to test the validity of its conclusion Add NAdd PAdd N,P Control

Randomization -Assign treatment randomly to an experimental group -Roll dice, random numbers table, Excel: “=rand()” function, Add NAdd PAdd N,PControl -Eliminate researchers’ bias or judgment

Why randomization and replication important? Reduce/eliminate self-deception and bias. Add NAdd PAdd N,P Control

Why randomization and replication important? Biased experimental design Add NAdd PAdd N,P Control

Graphs Title: The Effect of the independent variable on the dependent variable Independent Var (unit) Dependent Var (unit)

Title: The Effect of Elevated Nutrients on the Plant growth Soil Nutrients Control Add N Add P Add N, P Plant Biomass (g) Mean: shows differences between treatment groups. Error Bars: shows variability of data around the mean. Why control is important in this case?

Questions?

Communicating Scientific Finding

How do scientists communicate Science? Research Article Book News paper Website/Blog Presentation Meeting Lecture Interview (e.g. radio) Poster Lecture ppt Written CommunicationOral CommunicationVisual Communication

How do scientists communicate Science? Research Article Book News paper Website/Blog Presentation Meeting Lecture Interview (e.g. radio) Poster Lecture ppt Written CommunicationOral CommunicationVisual Communication

In Research Article, Presentation & Poster Abstract Introduction Methods Results Conclusions

Let’s have a mini-symposium! (20 min) a) Focal Poster -Presentation -Content b) Rest of the posters Which poster is most catchy/attractive? Why?

Poster Evaluation -Are research questions and hypotheses stated clearly? -Does poster communicate the importance of the study? -What are the dependent and independent variables? -Are the tables and/or figures used to present the data effectively? -Are the conclusions related back to the hypothesis, key scientific concepts, and background research?

Which poster is most catchy/attractive?

Communicating Science: Poster Presentation *Borrowed some materials from: LiLynn Graves Web and Graphic Designer, CCMR

Why poster? More interactive than writing a paper or giving a talk More time to talk with people Can hang on the wall You can be creative!

Poster is basically a summary/outline of a research paper

What to include? Title, name (Abstract) Background/Intro Methods Results Conclusion Acknowledgement (Citation)

Title – 1-2 lines Name and affiliations What to include

What to include (cont’d) Background -Why important/interesting -Hypotheses *Get your audience interested in your work Methods -Brief -Include photos and illustrate experimental design, if possible

What to include (cont’d) Results -Include tables, figures, stats and brief description. -Make sure your x and y axis are labeled clearly. -Keep it simple! Days Population Size Population size of Predator and Prey through Time Prey Predator

What to include (cont’d) Conclusions - Address your hypotheses - Discuss why your results are interesting/important - “big picture” - future direction (Literature cited) Acknowledgement

Title, name (Abstract) Background/Intro Methods Results Conclusion Acknowledgement (Citation)

Organization

Colors Be considerate for people with colour-vision deficiency

Poster in PowerPoint Determine the size of a poster File -> page setup 46 x 38 inches Font size no smaller than size 40

After you make a poster draft… Print out a letter size draft and edit, edit, edit! Get feedback from your teacher/mentor and peers “Peer Edit”

Peer evaluation? Get feedback from different people Good practice to give/receive constructive criticism Good motivation?

Questions, comments?