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 pea 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 trials. 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.

• a) The amount of sleep the night before is the independent variable as it is what researchers manipulate to see its effect on running speed.
• b) The type of asphalt is the independent variable as it is changed to observe its effect on gas mileage and wildfire incidence.
• c) The scraping with a band - aide is the independent variable as it is what is done to see its effect on healing time.
• d) The concentration of salt solutions is the independent variable as different concentrations are given to plants to see their effect on flower number.
• e) The salt water concentration is the independent variable as it is varied for sunflower plants to observe the outcome.
• f) The humidity level is the independent variable as it is different for the redwood trees to measure its impact on tree height.
• g) The location (inside greenhouse or outside) and water amount are independent variables for the redwood trees as they are changed to measure tree height. For pea plants, water amount is the independent variable as different amounts are given to see plant growth.
• h) The amount of water is the independent variable for pea plants as different volumes are provided to observe plant growth.
• i) The size of the soccer ball is the independent variable as different sizes are tested to see the time it stays in the air.
• j) The cleaning solution (spray half with solution and half with water) is the independent variable as it is changed to see the effect on removing slime.

Answer:

a) Amount of sleep the night before
b) Type of asphalt
c) Scraping with a band - aide
d) Concentration of salt solutions
e) Salt water concentration
f) Humidity level
g) Location (inside/outside), water amount for redwood trees; water amount for pea plants
h) Amount of water for pea plants
i) Size of the soccer ball
j) Cleaning solution (spray half with solution and half with water)