IV
Definition of an independent variable
The variable that is purposely manipulated or changed during the experiment.
Definition of the dependent variable
The response that can be observed or measured in an experiment.
Definition of a control group
The group that does not receive the treatment being tested.
The liquid is blue
Qualitative
A scientist changes the amount of water given to a plant and measures its height. What is the IV?
Amount of water
A scientist changes the amount of sunlight given to plants and measures how quickly the plant grows. What is the independent variable?
Amount of sunlight
A scientist changes sunlight and measures how tall plants grow. What is the dependent variable?
Plant height
A scientist tests a new fertilizer. Group A gets regular soil. Group B gets fertilizer. Which is the control?
Group A
The plant is 18 cm tall
A scientist changes the amount of water given to a plant and measures its height. What is the DV?
Plant height
A student tests three brands of paper towels and tests how much water them absorb. What is the independent variable?
Brand/type of paper towel
A student tests different paper towels and measures how much water each absorbs.
Amount of water absorbed
A scientist tests a new medicine. One group receives the medicine and one receives a placebo. Which is the control group?
Placebo group
The rock feels rough and has a gray color
Shannon wants to see if the amount of time she studies will affect her grades. She normally studies for 30 minutes a night, but decides to double her study time to one hour per night. Over the next three weeks, Shannon sees her science grade rise 10%.
Independent Variable =
Dependent Variable =
Control =
IV: amount of time studies
DV: grades
Control: normal 30 mins
A scientist changes the temperature of water to see how quickly sugar dissolves. What is the independent variable?
Water temperature
A scientist changes water temperature and records how many seconds it takes sugar to dissolve.
Time it takes sugar to dissolve
Why is a control group important?
It gives scientists something to compare their results to. The standard for comparison.
The sun set at 7:00 pm
Quantitative
Eric wants to see if a Shark vacuum works better than his current Dyson. He makes sure both of the vacuum canisters are empty, and then vacuums half of the living room with the Dyson and the other half with the Shark. After vacuuming, he measures the amount of dust in each canister.
Independent Variable =
Dependent Variable =
Control =
IV: Brand of vacuum
DV: Amount of dust
Control: Dyson
A scientist gives plants different amounts of fertilizer and counts how many flowers grow. Name the independent variable AND explain why.
Amount of fertilizer because it is what the scientist changes.
A scientist changes the amount of fertilizer and counts the number of leaves on each plant. What is the dependent variable AND why?
Number of leaves because it is what the scientist measures.
During our Nickel Lab we experimented soapy water in part 2. What would be our control group to this experiment?
The part A (water only group)
Definition of both Qualitative and Quantitative
Qualitative: observed w 5 senses
Quantitative: observed using calculations, measurements, and counting.
Chris wants to see if his basil plants grow better in full sunlight or partial sunlight. He plants 5 basil plants on the east side of his house that receive light only in the morning, and 5 more plants on the south side of his house that receive light all day. After a month, Chris measures the height of each plant.
Independent Variable =
Dependent Variable =
Control =
IV: amount of sunlight
DV: Height of plants
Control: NONE