Identifying Changed and Measured Variables

Cars get better gas mileage when their tires are properly inflated.

Sayeema wanted to test if this was true. She filled the tank in her car, correctly inflated the tires, drove her car, and then calculated the miles per gallon. The next time, she made her tires a little flat and drove over the same roads before calculating the miles per gallon. She tried one last time with tires that were inflated a little too much.

What is the Independent (changed) variable?

• gas mileage

• tire inflation pressure

• type of gasoline used

• roads where the car was driven

Music may help people relax.

Darius got two groups of people together. He took everybody's pulse and blood pressure. Then he allowed one group to listen to soothing music while the other group sat in silence. After the song was over, he measured everyone's pulse and blood pressure again.

What is the Dependent (measured) variable?

• sitting in music or silence

• pulse and blood pressure

• type of music

• Darius

Preservatives such as salt help keep food fresh.

Imaan made 18 loaves of bread using the same recipe and baking method. In nine of them, she used no salt. In the other nine, she used salt. After the loaves were baked, she placed each of the loaves in a plastic bag and left them close together on the counter in her kitchen. Each day she looked at them to see if any mold had started to grow.

What is the Dependent (measured) variable?

• location of bread on the counter

• amount of salt used in the bread

• mold growth on the bread in the bags

• number of loaves of bread

Emily made four paper helicopters. Each was made out of a different kind of paper. She flew each one several times in the hallway and recorded how long each stayed in the air.

What is the Independent (changed) variable?

• flight time

• number of helicopters

• type of paper

• hallway

Ethan filled cups of the same size with equal amounts of water. The groups were placed in five different locations around his house. After two weeks, he measured the remaining water to determine how much had evaporated, by measuring how much water was left in each cup.

What is the Dependent (measured) variable?

• location of cups

• amount of time they were left in locations

• amount of water still in cup

• size of cups

Whether paint is oil-based or water-based could determine how long it takes to dry. Liliana found two pieces of the same kind of pine wood and painted one with oil-based blue paint and the other with water-based blue paint. Then she timed how long it took for each piece to dry.

What is the Dependent (measured) variable?

• color of paint

• oil-based or water-based paint

• How long it took to dry

• kind of wood

Caffeine may make people more alert. Devin tested 100 people by using their scores in a video game. Fifty of the people drank a can of caffeinated soda before playing. The other 50 drank a can of caffeine-free soda before playing. He recorded each person's score on the game.

What is the Independent (changed) variable?

• amount of caffeine in the soda

• video game score

• amount of playing time

• number of people

Malcolm had always heard that plants grow better if you talk to them. He purchased 10 plants, measured the height of each one, and made two groups of plants that he kept in similar conditions. He talked to one group for a half an hour each day but did not talk to the other group. After three weeks, he measured and recorded the height of each plant again.

What is the Independent (changed) variable?

• talking or not talking to plants

• amount of plant growth

• number of plant groups

• kind of plants