Variables

An important piece of the

Scientific Inquiry Process.

Created by: Mrs. Gismonde

Variables

Variables are factors that change in an experiment.

Knowing how to identify the different types of variables is useful within in scientific method.

Variables are used in... Creating a hypothesis Designing an experiment Collect and analyze data Creating a conclusion

Variables There are three types of variables:

Test Variable Also know as: Independent Variable

Outcome Variable Also know as: Dependent Variable

Control Variable Also know as: Constants

Test Variable A test variable (independent variable) is an

item that scientists is testing or changing in an experiment.

There is only one test variable per experiment.

Example #1

Read the following paragraph: Dr. Smith wants to test wither a new drug

increases the maze running performance of older rats. Just like humans, older rats show signs of poorer memory for new situations. Dr. Smith teaches two groups of older rats to find a piece of cheese in the maze. One group of rats are given the new drug while they are learning the maze. The second group of rats are not given the drug. After one week of learning the maze, he retested the rats and recorded how long it took them to find the cheese.

Question #1 What is the test (independent) variable?

Hint: What was the researcher testing in this experiment?

a) Age of the rats. b) Type of maze. c) Length of time it took the rats to run the maz

e. d) Presence of new memory drug.

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Remember:The test variable is the item the scientists is

changing.

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To review… The test variable is the new memory drug.

The memory drug was the item that the scientist was testing on one group of rats.

Outcome Variable

The outcome variable (dependent variable) is a change that is observed and recorded throughout the experiment.

Scientists collected the outcome variable in the form of data. Data is typically collected in a data table.

There can be multiple outcome variables within an experiment.

Example #1

Review the following paragraph: Dr. Smith wants to test wither a new drug

increases the maze running performance of older rats (test variable). Just like humans, older rats show signs of poorer memory for new situations. Dr. Smith teaches two groups of older rats to find a piece of cheese in the maze. One group of rats are given the new drug while they are learning the maze. The second group of rats are not given the drug. After one week of learning the maze, he retested the rats and recorded how long it took them to find the cheese.

Question # 2 What is the outcome (dependent) variable?

Hint: What item did the researcher observe and record changing?

a) Age of the rats. b) Type of maze. c) Length of time it took the rats to run the maz

e. d) Presence of new memory drug.

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Remember:The outcome variable is the item that changed

because of the test variable.

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To review…

Remember the researcher was testing a new memory drug on one group of rats.

He believed that the new drug might decreased the time it took the mouse to complete the maze.

Therefore, this was the outcome variable.

We stated that the outcome variable is data that is collected in a data table.

Below is an example of a data table for the memory drug experiment:

You will learn more about data collection in the lessons to follow.

Data Table:Presence of new memory drug verses length of time rats took to

complete a maze.

(Test Variable)

New Memory

Drug

(Outcome Variable)

Length of time to complete maze (min/sec)

Trial 1 Trial 2 Trial 3 Average

Rats with memory

Drug

Rats without memory

drug

Controlled Variables The controlled variable is the item or group

that remains untested in an experiment.

The data from the control group will be compared to the data from the outcome variable.

There can be multiple constants within an experiment.

Example #1

Review the following paragraph: Dr. Smith wants to test wither a new drug

increases the maze running performance of older rats (test variable). Just like humans, older rats show signs of poorer memory for new situations. Dr. Smith teaches two groups of older rats to find a piece of cheese in the maze. One group of rats are given the new drug while they are learning the maze. The second group of rats are not given the drug. After one week of learning the maze, he retested the rats and recorded how long it took them to find the cheese (outcome variable).

Question #3 What is the controlled group within this

experiment? Hint: It is the group that remained the same?

a) Length of time it took the rats to run the maze.

b) Presence of new memory drug.c) Rats that were not given the new memory dr

ug.d) None of the above.

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Remember:The controlled variable is the group or items

that stay the same during the experiment.

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To review…

Scientists always need a control group in an experiment.

In this experiment the scientist could compared the maze times of the rats who took the memory medication to those who did not (control group).

Controlled Variables Within this experiment there were other

constants besides the group of rats not receiving the memory drug.

Can you think of any constants?

Possible answers could include: Same experimenter Same maze Same type of cheese given to each rat Same age of all the rats

The memory drug experiment paragraph did not include a conclusion.

Examine the data table below. Come up with a possible conclusion to the

memory drug experiment.

Presence of new memory drug verses length of time rats took to complete a maze.

New Memory Drug Length of time to complete maze (sec)

Trial 1 Trial 2 Trial 3 Average

Rats taking memory

drug

45 sec 55 sec 40 sec 46.7 sec

Rats not taking the memory

drug

60 sec 50 sec 75 sec 61.7 sec

Possible Conclusion: The scientist could infer his hypothesis was

supported because, the new memory drug decreased the older rats completion time through the maze. The data indicates that the rats in the controlled group took an average 61 seconds to complete the maze; while the rats using the new memory drug took 46 seconds to complete the maze. It appears as though the rats in the control group were 15 seconds slower through the maze then the rats taking the new drug.

Variables continued…

Identifying the different types of variables within an experiment is a difficult task.

In the next lesson you will learn how to write a hypothesis using the test and outcome variables.

Right now it’s time to test your knowledge on the different types of variables.

Problem #1Read the following paragraph: Homer notices that his shower curtain is

covered with a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower curtain with coconut juice. Homer needs a control group to compare the results of his experiment to. He decides to sprays the other half of the shower curtain with just water.

Question #1

Review: What was Homer initial question? Will coconut juice remove the green slime on his

shower curtain?

1) What was the test variable within this experiment?

a) Spraying coconut juice on half of the shower curtain

b) Change in the appearance of green slime on shower curtain

c) Spraying water on half of the shower curtain d) None of the above

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the paragraph.

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information on variables.

Great JobClick the beaker below to continue:

Problem #1Read the following paragraph: Homer notices that his shower curtain is

covered with a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower curtain with coconut juice. Homer needs a control group to compare the results of his experiment to. He decides to sprays the other half of the shower curtain with just water.

Return to Question

#1

Return to Question

#2

Return to Question

#3

Question #2

2) What was the outcome variable within this experiment?

a) Spraying coconut juice on half of the shower c

urtainb) Change in the appearance of green slime on s

hower curtainc) Spraying water on half of the shower curtain d) None of the above

Need Help?Click here to review

the paragraph.

SorryClick here to try again

Need Help?Click the picture below to read additional

information on variables.

Great JobClick the beaker below to continue:

Question # 3

3) Identify the control group within this experiment.

a) Spraying coconut juice on half of the shower curtain

b) Change in the appearance of green slime on shower curtain

c) Spraying water on half of the shower curtain d) None of the above

Need Help?Click here to review

the paragraph.

SorryClick here to try again

Need Help?Click the picture below to read additional

information on variables.

Great JobClick the beaker below to continue:

Problem # 1

Read the following paragraph: Results: After 3 days of spraying the shower

curtain with coconut juice and water, there is no change in the appearance of the green slime on either side of the shower curtain.

Question # 44) What would Homer’s conclusion be?

Possible answers: The coconut juice did not get rid of the green

slime on a shower curtain. When he analyzed his results he discovered there

was no difference between his test group (half of shower curtain sprayed with coconut juice) to his control group (half of shower curtain sprayed water).

Therefore coconut juice is not an effective treatment for the green slime on his shower curtain.

Watch it in action Click on the toaster below to watch a video clip

on yeast.

While your watching the video watch for the following items: Test Variable Outcome variable Conclusion

Questions What question did the scientist pose?

What does yeast like to eat?

What was the test variable? The different types of food the scientist feed the yeast.

What was the outcome variable? The amount of carbon dioxide produced by yeast as it

feed on the different types of food.

What was the conclusion of the experiment? Yeast prefers to eat sugar over salt, oil, flour and the

cookie. The scientist came to this conclusion by observing the amount of carbon dioxide produced by the yeast in each bag. In this particular experiment the yeast produced the most carbon dioxide when eating sugar.

Variables QuizDirections: Rewrite the sentences on the next slide on a

lined piece of paper. Place a T next to the true statements. Place an F next to the false statements.

If a statement is false change the underlined word(s) to make the sentence true.

Variables Quiz

1. True or False: The first step of the scientific method is testing a hypothesis.

2. True or False: A hypothesis is an educated guess.

3. True or False: Every experiment should have one test variable.

4. True or False: A control is a factor that is missing the outcome variable, but is the same as other factors in an experiment.

5. True or False: The outcome variable is a change that is observed and recorded within an experiment.

Bibliography Identify the controls and variables. (n.d.). Retrieved June 2011, from http://

www.biologycorner.com/worksheets/controls.html

Experimental designs. (n.d.). Retrieved June 2011, from http://clcpages.clcillinois.edu/home/soc455/psycweb/research/variables.htm

Southwest Center for Education and the Natural Environment . (n.d.). Retrieved June 2011, from Scientific method: http://scene.asu.edu/habitat/s_method.html

Wikipedia. (n.d.). Retrieved June 2011, from Homer Simpson: http://en.wikipedia.org/wiki/Homer_Simpson

Wikipedia. (n.d.). Retrieved June 2011, from Krusty the Clown: http://en.wikipedia.org/wiki/Krusty_the_Clown