Designing Experiments Stuff in Orange MUST be in your notebook

Background Info Mr. Harris was an awesome athlete in high school. He earned 12 sport letters and started for the varsity team on nearly every sport. Consequently, he spent lots of time in the gym and locker room. He would develop raging athlete’s foot infections – red, itchy, raised bumps all over his toes and feet. Yikes!

The Remedy One time, he was SO sick of itchy feet that he went to the store, spent $40 and bought every product they had for itchy feet: Special shoe insoles Powder for shoes Cream for feet Special infused socks Spray for feet Special ant-fungal soap He used every remedy for 3 days…

The $40 Question After 3 days, his feet were cured – no more red, itchy bumps! After football practice one day, his mom asked, “How are your feet?” He replied that they were fine now. Then she asked, “What did the trick?” What did he reply?

Change only ONE thing at a time Experimental Design He didn’t know what worked to kill his fungal infection because he tested too many cures at once. He did NOT use a fair test method. What SHOULD he have done? That “one thing” which is changed is called the Independent Variable. I remember this because I looks like 1. Change only ONE thing at a time

Change only ONE thing at a time Experimental Design When conducting a good experiment, we also have to come up with a way to measure the outcome. We could make qualitative measurements by counting the number of red dots or measuring the skin area which is red. Or we could make qualitative observations of the “deepness of red” or the itchiness. The measured outcome of the experiment is the DEPENDENT VARIABLE. I remember this because the outcome DEPENDS on the results. Change only ONE thing at a time

Take #2 The next time his athlete’s foot problem flared up, he knew what to do. He focused on just one cure. He decided to try rubbing antifungal cream onto the red bumps. He faithfully applied the cream twice per day to both feet. After 3 days, both feet were cured! Did he use a fair testing method this time?

Experimental Design In a good experiment, we always compare two or more groups. A “control group” is the name we give to this set of trials which are used as a baseline or a comparison. The control group is different from the test group in only one way – the Independent Variable. Most experiments have a control group, but not all. Compare two groups

Experimental Design Since the control group and the test group differ in only one way – the Independent Variable – all of the things they have in common are called CONSTANTS. CONSTANTS are the identical conditions for both the control group and the test group. For athlete’s foot the constants would be things like: both feet had the same amount of sweat both feet were the same temperature both feet was washed the same way both feet had the same amount of light exposure both feet had the same type of socks both feet had the same type of shoes Compare two groups

Take #3 This time, he was sure he knew what to do when the old red, itchy bumps came back. He used one foot as the control group, and did not put any “remedies” on that foot. On the other foot, changed only the independent variable. What does he know about the remedy if… If both feet are still red? If both feet are cured? If the control foot is red and the remedy foot is cleared?

Repeat at least three times Experimental Design If one application of Tinactin cream cures the spots on one foot, can we declare to the world that, “Tinactin cream is the best Athlete’s Foot remedy and should be used by all!” ? Do we have any certainty in our results if we conduct only one trial? Do you think that drug manufacturers test their product only one time? For 9th grade, we are going to require at least 3 repeats, with similar results. Repeat at least three times

First, ask a question What are the effects of ______ _____ ____ on puzzle completion speed? Write this in the “Question” box of your experiment report. A good experiment starts with a question that can be answered by doing an experiment. Do NOT ask a yes or no question.

Second, think about what you already know, or do literature research I know that… Write this in the “Background Knowledge” box of your experiment report. You need some background knowledge about a subject before you can make a prediction of the outcome. What do you already know about puzzles?

Third, make a prediction… If _______________ then the puzzle completion speed will __________. Write this in the “Hypothesis” box of your experiment report. Draw a sample graph of your prediction. Based on what you already know about puzzles, predict the answer to your question. Make a graphical prediction also. (A hypothesis is a prediction, not a guess)

Fourth, make this a “fair test”… What one thing will be changed? IV How will you measure the outcome? DV What two groups will you compare? Control What things will you keep the same? Constants Write these in the “Fair Test” box of your experiment report.

Last, make a step-by-step procedure Step 1: Gather 6 puzzles (one at a time) and a stopwatch. Step 2: Have the test subject sit at a table. Step 3… Decide how you will DO the experiment and what supplies you will need. Write this down as step- by-step instructions. Make the instructions detailed enough that a stranger could conduct the experiment.

Work with your group and complete the front side of your experiment report