1.1.R - Lesson: Independent and Dependent Variables
Scenario C
Grandma Hippity Hop is worried about the ice that will be forming on her sidewalk this winter. She doesn't have money to waste on sidewalk salt that is ineffective, so Brenda decides to do some testing for her.
Dependent variable (DV)
How long it takes for the ice to melt?
Variables
In a scientific experiment, only ONE variable will be changed at a time. If we change more than one factor we will not be able to tell what caused a change to occur. You only have one independent variable (IV). This is also called the manipulated variable (MV). This is the variable that YOU change. This is what you are testing. The control (controlled variable) is everything that remains the same in the experiment. This keeps the experiment fair and valid. The dependent variable (DV) is what we are trying to measure and what we are hoping responds to the IV. This is also called the responding variable (RV). The DV is dependent on the IV.
Scenario A
Jordan wants to see if earthworms prefer rough or smooth terrain to crawl through. What will be his independent variable? This is what he will change in his experiment.
Controlled variables
Jordan would buy all the same kind of worms. Not half red wigglers and half earthworms. Different species might prefer different kinds of terrain. The amount of water sprayed on all the worms should be controlled also. You wouldn't want some to dry up and die due to lack of water. That has nothing to do with the terrain. Besides, if you kill your worms during your experiment, the project is disqualified and you have to start all over again. No animal can suffer due to your experiment! Not even a lowly worm.
Controlled variables
Possible controlled variables: The ice cubes need to be exactly the same shape The ice cubes need to be exactly the same weight in grams The room temperature needs to be the same for all tests The person doing the test needs to wear the same rubber gloves during each test Anything else you can think of to keep the same
Controlles variable
Possible controlled variables: Time of day we feed Ling Ling The amount of food put in the dish each day should be kept the same Use the same dish every day Put the dish in the same place every day Keep the dog's daily schedule the same
Scenario B
Sally is having trouble with her dog Ling Ling, who will not eat the food put in her bowl. Sally wants to scientifically try three new brands to see if Ling Ling will be happier at dinner time. We can't ask Ling Ling which food she likes best and counting the times she wags her tail as she eats is not very scientific. We need to weigh the amount of food she eats each day and correlate it with the brand.
Independent variable (IV)
Terrain or what the worm is crawling over. Possible terrains include sandpaper, typing paper, silk, sand, and many others.
Dependent variable (DV)
The grams of dog food eaten of each brand (how much Ling Ling eats of each food).
Independent Variable
The one factor in an experiment that is changed or manipulated by the scientist.
Dependent Variable
The one factor in an experiment that you are trying to measure and is dependent on the independent variable; the factor that is responding to the independent variable.
Control Variable
The parts of the experiment that are not changed in any way; remain the same in an experiment.
Independent variable (IV)
Three brands of sidewalk salt
Independent variable (IV)
We are changing the brands of dog food so that would be the IV.
Dependent variable (DV)
We would not measure different amounts of water the worms have sprayed on them because that has nothing to do with the terrain. What about how far the worm crawls?
