Understanding Variables in Experiments

A student wants to test how the amount of sunlight affects the growth of a plant. She places one plant in full sunlight and another in partial sunlight, keeping all other conditions the same. What is the independent variable in this experiment?

• Type of plant

• Amount of sunlight

• Amount of water

• Height of the plant

Tags

NGSS.MS-LS1-5

NGSS.MS-LS2-1

In an experiment to see if fertilizer affects the number of tomatoes produced by a plant, what is the dependent variable?

• Amount of fertilizer used

• Number of tomatoes produced

• Type of soil

• Amount of sunlight

A scientist is testing the effect of different types of music on the growth rate of bacteria. What should remain constant in this experiment?

• Type of music played

• Growth rate of bacteria

• Temperature of the environment

• Amount of bacteria

A researcher wants to know if a new drug lowers blood pressure. She gives the drug to one group and a sugar pill to another group. Which group is the control group?

• The group receiving the new drug

• The group receiving the sugar pill

• Both groups

• Neither group

A student is testing whether the color of light affects the rate at which a plant grows. She uses red, blue, and green lights on different plants, but keeps the amount of water, soil type, and temperature the same. Which group is the experimental group?

• Plants under normal sunlight

• Plants under colored lights

• Plants with no light

• Plants with extra fertilizer

Tags

NGSS.MS-LS1-5

A class is investigating how the temperature of water affects how fast sugar dissolves. They use the same amount of sugar and water in each trial. Which of the following best describes the constants in this experiment?

• Temperature of water

• Amount of sugar and water used

• Time taken for sugar to dissolve

• Type of container

A scientist wants to test if a new fertilizer increases the height of bean plants. She uses two groups: one with the new fertilizer and one without. What is the best way to identify the dependent variable in this experiment?

• The variable that is changed by the scientist

• The variable that is measured as a result

• The variable that stays the same

• The variable that is not used

A student is testing how the amount of salt in water affects the boiling point. She adds different amounts of salt to separate pots of water and measures the temperature at which each boils. Which of the following is the independent variable?

• Amount of salt added

• Boiling point temperature

• Type of pot used

• Amount of water

A group of students wants to test if listening to music while studying affects test scores. They divide the class into two groups: one studies with music, the other without. They keep the study time and material the same. Which group is the control group, and why?

• The group studying with music, because they are exposed to the variable being tested

• The group studying without music, because they are not exposed to the variable being tested

• Both groups, because they are both being tested

• Neither group, because both are exposed to the same conditions

A researcher is testing the effect of different amounts of caffeine on reaction time. She gives one group no caffeine, another group a small amount, and a third group a large amount. All other factors are kept the same. How would you identify the experimental and control groups in this experiment, and what reasoning supports your answer?

• The group with no caffeine is the experimental group because they receive the treatment

• The groups with caffeine are the experimental groups because they receive the treatment, and the group with no caffeine is the control group because they do not receive the treatment

• All groups are experimental because they are all part of the experiment

• The group with the largest amount of caffeine is the control group because they receive the most treatment

Tags

NGSS.HS-PS1-5