Independent, Dependent, and Controlled variables

Independent Variable An independent variable is a factor that is changed in an experiment. What can I change?

Dependent Variable The dependent variable are changes that occur due to the independent variable. What do I observe?

Controlled Variable Parts that stay the same

Prediction Making an inference about an event based on evidence or past experience.

Example 1 A dentist wanted to determine which brand of toothpaste would make teeth whiter. He gave his patients Crest and Oral B. The patients brushed for the same amount of time, used the same amount of toothpaste and had their teeth checked each week. Independent variable___________________ Dependent variable _____________________ Controlled variable _____________________

Answers to Example 1 Independent variable Dependent variable Toothpaste Dependent variable Whiter teeth Controlled variable Same amount of toothpaste, same amount of time brushing their teeth, and getting their teeth checked.

Example 2 A scientist wanted to determine if eating carrots would help peoples vision. For each meal one group of people ate carrots while the other group didn’t. All of the people ate at the same time and place. Independent variable_______ Dependent variable ________ Controlled variable _________

Answers to Example 2 Independent variable Dependent variable Eating carrots Dependent variable Improved vision Controlled variable Eating at the same time and place

Example 3 Mrs. Sanders wanted to determine which of her two cars (Lamborghini and Porsche) had the best gas mileage. She drove each car to school and home for one week. She made sure to leave at the same time and travel the same way. Independent ____________________________ Dependent ______________________________ Controlled group __________________________

Answers to example 3 Independent: Dependent: Control group: Cars How the gas mileage is affected Control group: Traveled the same way Left at the same time

Example 4 A group of students were given a short class in speed-reading. The teacher was curious if money would help the students perform better on a reading test. Half the students were given $5 for doing well on the test, and the other half were not given money. All of the students took the same test and had the same amount of time to take the test. Independent _______ Dependent _______ Controlled group _______

Answers to Example 4 Independent: Dependent: Control group: Money How the students did on the test Control group: Same test Same amount of time to take the test

Example 5 A study was done to determine if the type of gasoline would affect the pollution produced by cars. Independent __________________ Dependent __________________ Controlled Group __________________

Answers to Example 5 Independent: Dependent: Control group: Gasoline Pollution Control group: All Cars Amount of gasoline

Write a hypothesis If the Bears practice for three hours each day, will they have a winning season?

Write a hypothesis If I eat a candy bar each morning for breakfast, will I have more energy in the morning?

Example 6 Mr. Schroeder wants to see if students who had a healthier lunch had an effect on how students do in school. Half of the sixth graders will eat a well balanced lunch and the other half will eat whatever they want. They will be given the same amount of food and the same amount of time to eat. Independent variable____________________ Dependent variable ____________________ Controlled variable _____________________

Answers to Example 6 Independent variable Dependent variable Type of lunch Dependent variable Perform better in school Controlled variable At the same place Same amount of food

Example 7 A student wanted to test if the amount of gears affected the speed of their bike. The student added gears after each mile he traveled. After each gear was added, he would ride the bike one mile. Independent variable____________________ Dependent variable ____________________ Controlled variable _____________________

Answers to Example 7 Independent variable Gears Dependent variable How fast the bike will go Controlled variable Same bike The bike is being tested by the same person

Example 8 The amount of carbon dioxide given off by buses was measured by using different amounts of Ethanol gasoline. Independent variable____________________ Dependent variable ____________________ Controlled variable _____________________

Answers to Example 8 Independent variable Ethanol Gasoline Amount of dioxide Controlled variable Busses Ethanol gasoline

Example 9 A farmer wanted to measure the different types of water that would help plant growth. The plants were all the same and planted in the same area. They received the same amount of water and sunlight. Independent variable____________________ Dependent variable_____________________ Controlled variable _____________________

Answer to example 9 Independent variable Different types of water Plant growth or the height of the plants Controlled variable All the plants were the same type Plants were planted in the same area Received the same amount of water Received the same amount of sunlight

Example 10 A teacher wanted to determine if students who had a good night sleep did better on tests. Half of the students had 8 hours of sleep while the other half of students had 6 hours of sleep. All of the students woke up at the same time and took the same test. Independent variable____________________ Dependent variable _____________________ Controlled variable _____________________

Answers to example 10 Independent variable Dependent variable Amount of sleep students had Dependent variable Better performance on tests Controlled variable The students woke up at the same time The students took the same test

Example 11 A scientist wanted to determine if the type of liquid helped plants grow the highest. All of the plants were the same type and given the same amount of liquid. Some plants were given Red Bull, Vitamin Water, or water. Independent variable ___________________ Dependent variable ____________________ Controlled variable _____________________

Answers to example 11 Independent variable Dependent variable Types of liquid Dependent variable Plant growth Controlled variable All the the plants were given same amounts of liquid Same plants