Independent/Dependent Variables - Miss Schaefer's Science Grade 8

Notes- Independent/Dependent Variables
Variable- Something that is changed.
In scientific experiments there are two variables- One that you control and one that is the result.
Independent Variable- “The Cause”
The one thing that is changed in an experiment
This variable makes one test “independent” of another test
On a graph it is on the x-axis(along the bottom)
Dependent Variable- “The Effect”
The result of the experiment
What is measured
This “depends” on what you changed
On a graph, it is on the y-axis(along the vertical side)
******The independent variable causes the dependent variable to change******
In the following statements, identify the independent and dependent variables
1. The temperature of the water was measured at different depths of the lake.
Two things were changed in this statement. The first was the depths and the second was the temperature
Plug these into the bolded statement: The different depths causes the temperature to change.
This is correct, because we know that the water temperature gets colder the deeper you go.
IV: depths
DV: temperature
2. The amount of time you study will make a positive difference on your next test score.
Two things are changed:
1. Time spent studying
2. Score on next test.
The time studying causes the score on the next test to change.
This is correct, because we know the longer you study for a test, the higher your grade will be
IV: time studying
DV: score on next test
3. Lemon trees receiving the most water produce the largest lemons
The water causes the lemons to change.
IV:amount of water DV: size of the lemons
Independent and Dependent Variables- Identify the independent and dependent variables in each sentence
1. The higher the temperature of water, the faster the egg will cook
The temperature causes the egg to change.
IV: temperature
DV: how quickly the egg cooks
2. An investigation was done to see if keeping the lights on for different amount of time each day affected the
number of eggs the chicken lay.
The light causes the eggs to change.
IV: amount of light
DV: number of eggs
3. The time it takes to run a mile depends of the amount of exercise a person gets.
The exercise causes the time to change.
IV: amount of exercise
DV: amount of time
4. Grass will grow taller if it is watered and fertilized more.
The height causes the water and fertilizer to change. The water and fertilizer causes the height change.
IV: water and fertilizer DV: height of grass
5. An investigation was performed to see if corn seeds would sprout at different times depending on the
temperature of the air in which they were placed.
The seeds cause the air temperature to change. The air temperature causes the seeds to change.
IV: air temperature
DV: time seeds sprout
6. The amount of algae growth in lakes seems to be directly related to the number of sacks of fertilizer sold.
The algae growth causes the fertilizer to change. The fertilizer causes the algae growth to change.
IV: amount of fertilizer sold
DV: amount of algae growth
7. The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead.
The pollution causes the gasoline to change. The lead in gasoline causes the pollution to change.
IV: amount of lead in gasoline
DV: amount of pollution
8. Students in science class carried out an investigation in which a flashlight was pointed at a screen. They wanted
to find out if the distance from the light to the screen had any affect on the size of the illuminated area.
The distance causes the illumination to change.
IV: distance from the light DV: size of the illuminated area
9. The score on the final test depended on the number of study questions the student completed.
The score causes the number of questions to change. The number of questions causes the test score to change.
IV: number of questions
DV: test score
10. A study was done with white rats to see of the number of offspring born with birth defects was related to the
number of minutes of exposure to x-rays by the mother rats.
The offspring causes the minutes of exposure to change. The minutes of exposure causes the offspring to change
IV: minutes of exposure DV: birth defects in offspring
11. Five groups of rats are fed identical diets except for the amount of vitamin A that they receive. Each group gets
a different amount. After 3 weeks on the diet, the rats are weighed to see if the amount of vitamin A received
has affected their weight.
The vitamin A causes the weight to change.
IV: amount of vitamin A DV: rat’s weight
12. The state agriculture department has been counting the number of foxes in Brown county. Will the number of
foxes have any affect on the rabbit population?
The foxes cause the rabbits to change.
IV: number of foxes DV: number of rabbits