Controlled Experiments

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# Controlled Experiments - PowerPoint PPT Presentation

Controlled Experiments. Types of Variables Controlled Experiments. I. Types of Variables. Variable – anything that can be expected to change during an experiment Manipulated (Independent) Variable – the value of this variable is chosen by the person doing the experiment

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## PowerPoint Slideshow about 'Controlled Experiments' - mollie-burks

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### Controlled Experiments

Types of Variables

Controlled Experiments

I. Types of Variables
• Variable – anything that can be expected to change during an experiment
• Manipulated (Independent) Variable – the value of this variable is chosen by the person doing the experiment
• Typically you change something and then measure something else. The thing you change is the manipulated variable.
• Responding (Dependent) Variable – this variable is measured as the outcome of the experiment, it “responds” to changes in the manipulated variable
Comprehension Check
• Dr Leslie Gray is performing an experiment to determine what affect a car’s speed during a crash has on the amount of force that is exerted on a person’s head. To conduct the test she installs force sensors on the heads of her crash test dummies and crashes a car into a wall at 10mi/hr, 30mi/hr, 50mi/hr, and 70mi/hr. After each crash, she measures the amount of force that was exerted on the dummy’s head.
• What is the manipulated variable in her experiment?
• The speed of the crash
• What is the responding variable in her experiment?
• The amount of force on the head
II. Controlled Experiments
• In a controlled experiment there is only one manipulated variable, that is, you only change one variable.
• Because we only change one variable at a time, controlled experiments allow us to identify exactly which variables affect the outcome of an experiment
• All other variables must remain constant and are called control variables
• Caution – the word control has a different meaning in science than it does in conversation
Comprehension Check
• Julia is conducting an experiment to determine how the amount of water in a pan affects the amount of time it takes to boil the water. She started with 100mL of water and then times how long it took to boil the water. She repeated the procedure increasing the amount of water by 50mL each time.
• What is the manipulated variable?
• The amount of water is the MV.
• What is the responding variable?
• The time it takes to boil the water is the RV.
• List at least three relevant variables that must be controlled.
• Heat of stove, type of pan, size of pan, type of water, covered or uncovered, etc.