 Ask a Question: Testing the relationship between two measurable variables › Ex: Which species of fish grows faster when fed the new mirigrow fish food?  Do Research: Collect facts about all of the different species of fish, the claims of the mirigrow fish food, the habitats and lifestyle of fish…

 If…  Then…  Because….  Other Variables?

Today, we are going to talk about the main parts of a good experiment… Hint: It’s not blowing up our classroom!

 Let’s say that Brad has a pimple. He wonders what will get rid of it. He’s heard that putting toothpaste on the zit will get rid of it. He’s also heard that lemon juice will get rid of it. He decides to rub his face with lemon juice and toothpaste. The next morning his pimple is gone. But which thing cured him? The toothpaste or the lemon juice?

 How many of you think it was the toothpaste? Raise your hand.  How many of you think it was the lemon juice? Raise your hand.  The truth is….  THERE IS NO WAY FOR YOU TO KNOW FOR SURE BECAUSE THIS IS A BAD EXPERIMENT!!!

1) Independent variable 2) Controls 3) Dependent variable So What Are These?

 Control(s): what you keep the same so it/they don’t interfere with your independent variable  Variable: anything in an experiment that can change a. Independent variable: what you change on purpose in an experiment. (CAUSE) b. Dependent variable: what happens or changes in an experiment because of the independent variable (EFFECT)

Larry was told that a certain muscle cream was the newest best thing on the market and claims to double a person’s muscle power when used as part of a muscle-building workout. Interested in this product, he buys the special muscle cream and recruits Patrick and SpongeBob to help him with an experiment. Larry develops a special marshmallow weight- lifting program for Patrick and SpongeBob. He meets with them once every day for a period of 2 weeks and keeps track of their results. Before each session Patrick’s arms and back are lathered in the muscle cream, while Sponge Bob’s arms and back are lathered with the regular lotion.

 Larry is wondering how different lotions will affect how much Spongebob and Patrick can lift.  He manipulates the type of lotion that each person gets.  Therefore, the independent variable in this example is LOTION TYPE.

 In this experiment, there are several things that Larry kept the same: 1) He had Spongebob and Patrick do the same workout 2) He had both of them do the workout every single day for 2 weeks 3) He rubbed the lotions on their arms and back

 Since Larry is looking to see if the cream has an effect on how much someone can lift, the dependent variable is THE NUMBER OF MARSHMALLOWS THAT CAN BE LIFTED by Spongebob and Patrick  The number of marshmallows each one can lift depends on the type of lotion they got (independent variable)

Patrick believes that fish that eat food exposed to microwaves will become smarter and would be able to swim through a maze faster. He decides to perform an experiment by placing fish food in a microwave for 20 seconds. He has the fish swim through a maze and records the time it takes for each one to make it to the end. He feeds the special food to 10 fish and gives regular food to 10 others. After 1 week, he has the fish swim through the maze again and records the times for each. What’s the dependent variable? What’s the independent variable? What are some things he did or should control?