Workshop #3: Crea/ng an Excep/onal Science Fair Project – Experimental Design Project Organiza/on Hypothesis Experimental design, methods and materials Data Analysis Discussion Purpose Background Informa/on Results and Data Conclusions References Experimental Design: Scou/ng Experiments •
Before inves/ng a great deal of /me building an apparatus or laying out elaborate plans it is a good idea to do some quick experiments to show the feasibility of the concept and experimental method. •
Scien/sts who learn from there mistakes quickly are the most successful. Do not be afraid to change approaches or modify the goals of your project based on your scou/ng experiments. Example: Your hypothesis is that reducing the air pressure in a soccer ball will result in shorter kicks. Before building an automa/c soccer ball kicking machine to quan/tate the effect, try a few kicks with underinflated balls to be sure the trend is as you hypothesized. Experimental Design: Scien/fic Credibility •  Only change one parameter in each set of experiments (temperature, /me, concentra/on etc.) •  Control or record as many environmental condi/ons as possible •  Determine the precision of your measurements by repea/ng your experiments. •  When possible run a reference experiment. This is usually called a control. Experimental Design: Sand Dune Example “My hypothesis is that the sand par/cles are smaller on the leeward side of the dune and bigger on the windward side. The smaller par/cles are blown up the windward side to the top of the dune and over to the leeward side, where they pile up leaving the larger par/cles behind.” Experimental Design: Sand Dune Example “My hypothesis is that the sand par/cles are smaller on the leeward side of the dune and bigger on the windward side. The smaller par/cles are blown up the windward side to the top of the dune and over to the leeward side, where they pile up leaving the larger par/cles behind.” The sand was collected by star4ng at the bo7om of each sand dune and taking a 1mL sample in a small vial from the surface. The eleva4on (determined with a GPS), dune #, the side of the dune and any comments were recorded on a sheet that was a]ached to my clipboard. Then I walked up to the middle of the dune and did the same thing with the next vial. I then took a sample off each side of the top of the dune. I did the same thing down the other side. A^er tes/ng a few sand dunes I climbed up the ridge of a very tall dune and collected samples. On one dune I collected 5 samples at each posi4on for precision measurements. Experimental Design: Precision “In this sec/on the precision was determined of the grain size and color measurements. To determine the precision, 5 samples were taken from the same area on the bo]om of one sand dune. Then 20 grains were measured from each of the five samples for color and size. The average values were determined. This data is found in the tables below.” The conclusion was that unless more sand grains were counted to improve the precision of the measurements, only very large differences in the sizes and colors would be detectable. Experimental Design: Precision The differences in the samples are large enough to draw conclusions without increasing the precision of the data! Windward Top Leeward Top Grain Size in Microns Windward Bo]om Experimental Design: Running a Control •  A control experiment is used to validate that your experimental method produces results that agree with generally known results. Example: Your hypothesis is that growing radishes aeroponically hanging in air will elongate them. As a control you need to grow them in soil to be sure the bag of seeds you have produces round radishes. Control Hanging Experimental Design: Review •
If possible do some scou/ng experiments to validate you are on the right track. •
Design a set of experiments where only one variable is changed at a /me. •
Control as many environmental condi/ons as possible •
Do a sufficient number of replicates to demonstrate the variability in your measurements does not invalidate your results! •
Run a reference or control when possible Methods and Materials Sec/on •
Write a brief descrip/on of the experimental methods •
Describe any apparatus that is going to be built, use drawings and pictures •
Explain the variable tested in each experiment •
Explain the parameters held constant •
Explain how many replicates will be run and why. •
Describe the control experiments you will use. •
Make a list of the equipment and materials used Materials • Me]ler AE 50 scale • Barnant co. 400-­‐2901 vacuum-­‐pressure pump • Clear green helium balloons (17) • Texas Instruments Ti-­‐89 /tanium edi/on graphing calculator • Microso^ Office 2000 small business edi/on • Dell dimension 8100 computer • Printer paper (For calcula/ons, 21 sheets) • Black pen • Blue pen • Purple marker • Sharpie (silver, blue, green, black) • Helium Gejng Started with Your Experiments •  Use a notebook to record observa/ons and data. •  Take pictures as you work, they will make your project more interes/ng and help fill in the board. •  Be flexible, learn from your discoveries and modify your project as necessary. •  Enter your data into spreadsheets and plot out the results frequently to be sure everything makes sense.