Question

identify the independent variable in each of the following cases by highlighting the associated part of the statement.
a) athletes who do not get enough sleep the night before will not run as fast the next day.
b) researchers want to know if the gas mileage of cars will increase with a new type of asphalt.
c) the amount of rainfall in an area lowers the incidence of wildfires.
d) covering a scrape with a band - aide decreases healing time.
e) different rose bushes are grown in a greenhouse for two months. the number of flowers on each bush is counted at the end of the experiment.
f) you water three sunflower plants with salt water. each plant receives a different concentration of salt solutions. a fourth plant receives pure water. after a two - week period, the height is measured.
g) three redwood trees are kept at different humidity levels inside a greenhouse for 12 weeks. one tree is left outside in normal conditions. the heights of the trees are measured once a week.
h) pea plant clones are given different amounts of water for a three - week period. the first pea plant receives 400 ml of water a day. the second plant receives 200 ml of water a day. the third pea plant receives 100 ml of water a day. the fourth pea plant does not receive any extra water - only receiving water in natural ways. the height of the pea plants are recorded daily.
i) goldfish are fed varying amounts of food during a six - week study. one tank of goldfish is fed the normal amount of food once a day. a second tank is fed twice a day. a third tank is fed four times a day. the fishs weight is recorded daily.
j) you decide to clean the bathroom, and notice the shower is covered in a strange green slime. you try to get rid of this slime with different cleaning solutions. you spray half of the shower with the leading cleaning solution and spray the other half of the shower with water. after three days of spraying equal amounts of solution three times a day, the appearance of the shower is recorded.
k) you want to test which size soccer ball is easiest to juggle with your feet. you test a size 3, size 4, and size 5 ball. you count the seconds the ball stays in the air for each of the trails. you allow yourself to use your feet and head only to juggle the ball.

Explanation:

An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable. In each case, we identify what is being manipulated.
a) The amount of sleep is what is being considered as a factor that can be more or less for athletes, thus it is the independent variable.
b) The type of asphalt is what researchers are changing to see its effect on gas mileage, so it is the independent variable.
c) The amount of rainfall is what can vary and affect the incidence of wildfires, making it the independent variable.
d) Whether a scrape is covered with a band - aide or not is the variable being manipulated, so it is the independent variable.
e) The different rose bushes are the subject of the experiment, but the factor being manipulated is not clear. However, if we assume different types of rose bushes are being compared, that would be the independent variable.
f) The concentration of salt solutions is what is being changed for each sunflower plant, so it is the independent variable.
g) The humidity levels are what are being varied for the redwood trees inside the greenhouse, so it is the independent variable.
h) The amount of water given to each pea plant clone is what is being changed, so it is the independent variable.
i) The amount of food given to each tank of goldfish is what is being varied, so it is the independent variable.
j) The type of cleaning solution (leading cleaning solution vs water) is what is being changed to see its effect on the appearance of the shower, so it is the independent variable.
k) The size of the soccer ball is what is being changed to test ease of juggling, so it is the independent variable.

Answer:

a) Amount of sleep
b) Type of asphalt
c) Amount of rainfall
d) Use of band - aide
e) Type of rose bush
f) Concentration of salt solutions
g) Humidity levels
h) Amount of water
i) Amount of food
j) Type of cleaning solution
k) Size of soccer ball