The Scientific MethodVariables

(Physics Unit 1)

What is a variable?

What types of variables are there?

Variables

Controlled(Do not change)

Independent(Manipulated)

Dependent(Responding)

Independent Variable (manipulated)

The variable that is manipulated or changed in an experiment.

• The one you control and change.

• What you did. The treatment

• The Cause”

• Plotted on the x-axis on a graph.

Dependent Variable(Responding)

The variable that responds to changes in manipulated variable.

• What you measure or observe

• What happened

• “The Effect”

• Plotted on the y-axis on a graph.

Controlled Variables

Things we keep the same in an experiment, since we are not testing or measuring a response in them.

• Things you keep constant, don’t change during an experiment.

• The constants during an experiment.

Example of Identifying Variables in an Experiment

• A student was investigating the things that affected how candy dissolved in water. They wished to determine how the size of the candy pieces affected the time it took them to dissolve.

IV - How big the pieces are (cause)DV - Time to dissolve (effect)CV - Amount of water

- Temp of water- Time of stirring- How hard stirred- Type of container

2nd Example

• Does an electric motor turn faster if you increase the voltage?

IV - Voltage of the electricity measured in volts

DV - Speed of rotation measured in revolutions per minute

CV - Same motor for every test Time motor is on Work

3rd Example

• How fast does a candle burn? ?

IV - Time measured in minutes DV - Height of candle measured in

centimeters at regular intervals of time (for example, every five minutes)

CV - Use same type of candle for every test Wind--make sure there is none Temperature

Experimental Design

How do you set up an experiment?

An experiment is designed to test if a hypothesis is correct or not.

An easy way to do this is make a comparison between two groups, the experimental and control groups.

Experimental Group:

• The group which is experiencing the treatment you are testing.

• The part of the experiment in which you change a factor (variable).

Control Group:

• is a standard against which any change can be compared and measured

• The group in which no changes are made. You compare this group against the experimental group.

Scientific Method:

• A formalized process of investigation designed to solve a problem, which incorporates the testing of a hypothesis.

The Steps of the Sci. Method

• 1st Identify the problem - by asking questions

• 2nd Educate yourself about the problem, research the problem.

- library- reference books, magazines - ask the experts- internet, web sites, news groups

• 3rd Hypotheses, educated guess- always stated as an

“if-then” statement

• 4th Experiment- collect and record data

• 5th Analysis of data- stat’s

(average, mean, median, mode, range, etc.)

- graphs

• 6th Conclusions- Was your hypothesis correct or

not.- What does it mean?

• 7th Applications of findings

• 8th Communicate Findings