Athlete’s Foot and the Fair Test 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 skin infections – red, itchy, raised bumps and peeling skin all over his toes and feet. These infections were Athlete’s Foot – caused by a fungus on skin that loves to grow in damp, warm conditions. It also spreads rapidly on shower floors an can live in shoes. 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? 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, he was cured! Did he use a fair testing method this time?

Experimental Design Compare two groups 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. Most experiments have a control group, but not all. 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, he tested only one remedy at a time. 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? Repeat at least three times

Repeat after me…

Experiment Vocabulary copy these into your notes independent variable (IV) the one thing changed on purpose dependent variable (DV) the measured outcome of the experiment controlled variable (CV) something kept the same for all groups control group the half of the experiment trials used for comparison hypothesis a prediction of the outcome of an experiment based on prior knowledge

Show me that you know… What is IV? What is DV? What are CVs? Control? A snowboarder wants to know if waxing the bottom of her snowboard really makes a difference in her downhill speed, like she has heard. She takes her board (with no wax on the bottom) and lets it slide down the kiddie hill three times, recording how long it takes each time and starting at the same spot each time. Next she puts wax on her board and lets it slide down the same hill three more times, recording how long it takes each time and starting at the same spot each time. What is IV? What is DV? What are CVs? Control? Hypothesis? Number of trials?

Show me that you know… What is IV? What is DV? What are CVs? Control? A kid heard that hot water would freeze faster than cold water, but that just didn’t make sense, so he decided to conduct an experiment. He took 3 Styrofoam cups and filled them with exactly 500 mL of tap water then he put 500 mL of steaming hot water into 3 more Styrofoam cups. He placed all 6 cups into the freezer and checked them every 10 minutes to see if the top had formed an unbreakable solid by trying to poke a straw to the bottom of the water. What is IV? What is DV? What are CVs? Control? Hypothesis?

Show me that you know… You stay up at night reading with a flashlight and you want to know which batteries to buy to give you the most reading time. You have heard that Duracell ® is the best, but they are pricey! You buy two D batteries each of Duracell ®, Energizer ®, Rayovac® and Kirkland® brands. You get 4 identical flashlights out of your emergency kits and put one brand of batteries into each flashlight. You turn them all on at the same time one night in your room and wait to see which flashlight stays on the longest. What is IV? What is DV? What are CVs? Control? Hypothesis? Did you conduct enough trials?