Experimental Design

Experimental Design Hypotheses

Objectives • Become proficient at writing problem statements, hypotheses, and experimental procedures. • Identify independent variable, dependent variables, and controls when exposed to a scientific experiment. • Describe the correct way to gather data in an experiment.

What Do You Know? • What is a hypothesis?

Hypothesis • What is a hypothesis? • A hypothesis statement is: • A proposed answer to a problem. • Based on observations. • Testable (must be able to measure what is being tested). • Do not define a hypothesis as: • An “educated guess” • An “if-then” statement

Hypotheses • If a hypothesis is a PROPOSED answer to a problem, you cannot be afraid to be incorrect. "It is very unnerving to be proven wrong, particularly when you are really right and the person who is really wrong is proving you wrong and proving himself, wrongly, right." -Lemony Snicket

Things That Have Been Wrong Facts you have learned you’re entire life: • There are nine planets in our solar system.

Things That Have Been Wrong Facts you have learned you’re entire life: • There are 109 elements.

Things That Have Been Wrong • “Television won’t last. It’s a flash in the pan.” — Mary Somerville, pioneer of radio educational broadcasts, 1948.

Things That Have Been Wrong • “Heavier than air flying machines are impossible.” — New York Times, 1936 Hyperlink

Things That Have Been Wrong • "Everything that can be invented, has been invented." -- Charles H. Duell, Commissioner, U.S. Office of Patents, 1899.

Writing Hypothesis • NEVER USE, “I think” in a hypothesis. • You can use an if/then statement… but it is not necessary. Let’s look at the Same examples we Used yesterday

First Example Catalase is a substance that breaks hydrogen peroxide down into water and oxygen gas. You can measure the amount of oxygen to give you an idea of how fast the reaction is taking place. Temperature can affect the rate of hydrogen peroxide decomposition by catalase. Hypothesis as if/then:

First Example Catalase is a substance that breaks hydrogen peroxide down into water and oxygen gas. You can measure the amount of oxygen to give you an idea of how fast the reaction is taking place. Temperature can affect the rate of hydrogen peroxide decomposition by catalase. Hypothesis not as if/then:

Second Example – You Try! Victor notices some mold on a piece of bread he found in the back of cupboard. After investigating the mold he wonders if putting bread in a humid location would allow more mold growth.

Anything for the good of the cause? • Set up lab, you may get dirty. • No complaining, you’re not this guy Closure

Experimental Design