Scientific Method

What is the scientific method?

The scientific method is the basic method, guide, and system, by which we originate, refine, extend, and apply knowledge in all fields.

An organized approach that characterizes science

How do we (scientists) answer questions about the world?

The Scientific Method

Independent and Dependent Variables

Independent Variable (IV) Dependent Variable (DV)

The condition being studied The condition being affected by the IV

Controlled by the researcher Cannot be controlled by the researcher

Independent Variable Example Dependent Variable Example

Cause Effect

Before After

Input Output

What you do What happens

Activity Explain how you would test one of the

following questions using the scientific method: Are male manatees always larger than female

manatees?

Does caffeine make people hyper?

Does studying more help students to do better on tests?

Is penicillin a more effective antibiotic against E. coli than tetracycline?

Forming a HypothesisReminder:

Your hypothesis must be an IF….THEN…..BECAUSE statement.

It must contain an independent variable and a dependent variable.

Must be a testable statement.

Independent Variable (IV) Dependent Variable (DV)

The condition being studied The condition being affected by the IV

Controlled by the researcher Cannot be controlled by the researcher

Independent and Dependent Variables

The variable which depends on the other

variable is the: Dependent VariableThe variable being tested in a scientific

experiment

The other variable which doesn’t depend on

anything is the: Independent Variable

The variable that is changed to test the effects

Independent and Dependent Variables

Independent Variable Dependent Variable

Cell phone minutes used Cell phone bill

Amount of gas you have How far you drive

Number of assignments you turn in

Your 9 week grade

Number of hours you work How much money you earn

Miles over the speed limit Cost of a speeding ticket

How fast you drive Time it takes to drives somwhere

Who scores the most points in football

Result of a football game

Hypothesis – “IF” Statement

Begins with “IF” statement

The “If’’ Statement Start your sentence with “if”

Write down one of your variables

Add a connecting statement

Is related to

Is affected by

Causes

Write down the other variable Ex. IF water is related to plant growth,…..

Hypothesis – “THEN” Statement

The “Then”Statement

Write the word THEN

Make a comment about the relationship between the two variables EX. THEN the more you water plants, the

bigger they will grow

Hypothesis - Because Last part of hypothesis is BECAUSE

WHY based on REASON.

Add to end of hypothesis. Ex. IF water is related to plant growth, THEN

the more you water plants, the bigger they will grow BECAUSE water is necessary for plants to undergo photosynthesis.

Hypothesis - Summary

If __IV___ (connecting statement)__DV___, then (comment about how the variables relate), because….(why based on reason).

Connecting statements: Is related to

Is affected by

Causes

Examples IF skin cancer is related to ultraviolet light,

THEN people with a high exposure to UV light will have a higher frequency of skin cancer because UV radiation causes DNA mutations.

IF the frequency of winning the lottery is related to the frequency of buying lottery

tickets, THEN the more lottery tickets that you buy the better your chance of winning because of probability.

Hypothesis Writing Practice!

1. Chocolate may cause pimples.

2. Salt in soil may affect plant growth.

3. Bacterial growth may be affected by temperature.

4. Temperature may cause leaves to change color.