POWER-UP

Compare and contrast: Quality and Quantity

Explain what a cause and effect relationship is without using the words “cause” and “effect”

Variables Notes

Definition

A variable is something that can be changed

3 TYPES

Independent variable

Dependent variable

Constant variables

INDEPENDENT VARIABLE

It is the “cause” of the experiment

The scientist manipulates this variable

Is not changed by anything but the scientist

Abbreviated IV

DEPENDENT VARIABLE

This variable is the “effect” of the experiment

The scientist gathers data on this variable

Responds to the independent variable

Abbreviated DV

CONSTANT VARIABLE

This variable the scientist keeps the SAME

If it changes the rest of the experiment is messed up

Constant means NOT CHANGING

Abbreviated CV

IV & DV

The DV reacts to the IV

The IV changes the DV

There can be only 1!

There is only 1 independent variable

BECAUSE If there were more than 1 IV we wouldn't know what

the DV is responding to

And then we don't learn anything from the experiment

The importance of CV's

Without constant variables we don't know what the DV is responding to

The only thing that can change in an experiment is the IV

Everything else must be kept the same, so they are CV's

CV's ARE EVERYWHERE!

A CV is anything that is NOT: The IV The DV The scientist The unit of measurement The tools used

Just about everything else is a CV because we want to keep it constant so it doesn't mess up our data.

practice

Scientists were wondering if the color of a vegetable determined how healthy that vegetable is to eat.IV:DV:CV:CV:

OBSERVATION NOTES

Definition

An observation is information gathered with your five senses and/or tools.

2 types of observations

Qualitative

quantitative

QUALITATIVE OBSERVATION

Information gathered with the senses without measuring – no numbers just ADJECTIVES

EXAMPLES

Color

Texture

Taste

sound

QUANTITATIVE OBSERVATION

Information gathered by measuring – numbers

“N is for numbers”

EXAMPLES

Distance

Volume

Weight

Time

QUALITY

QUANTITY

What type of observation is made with the following statement?

“The hawk population has increased 308% over the past 10 years.”

Quantitative, because a measurement was made

What type of observation is made with the following statement?

“The house smells like gingerbread.”

Qualitative, because no measurement was made

practice

Scientists were wondering if the speed of a car was changed by the type of fuel in the car.IV:DV:

Type of observation needed:why?

Inference:An explanation, assumption, or prediction based on an observation made using prior knowledge

Prior Knowledge

Information you already know based on experiences you have had

Examples of Inferences•The plant grew tall because it was exposed to lots of sunlight.•Those appear to be goose tracks in the mud next to the pond.

Hint that a statement is an inference and not an observation:The statement contains the word “because”

It makes a prediction; future tense

It makes an assumption

Identify the following statements as qualitative observations, quantitative observations, or inferences. Explain your choice.

“The beaker contains 5 ml of water from the pond.”

Quantitative observation because a measurement was made

Identify the following statements as qualitative observations, quantitative observations, or inferences. Explain your choice.

“The water is cloudy because it came from the pond.”

Inference, because it is an explanation made using prior knowledge

Identify the following statements as qualitative observations, quantitative observations, or inferences. Explain your choice.

“The water from the pond contained organisms that were seen with the microscope.”

Qualitative observation, because no measurements were made

Make an observation of the picture.

Use your observation to make an inference.

What prior knowledge did you use to make that inference?