What makes a controlled experiment different from other scientific investigations, such as a systematic observation?

• It allows the investigator to make a claim based on evidence gathered during the investigation.

• It uses scientific methods of research to reach a conclusion about the topic of study.

• It provides the investigator with a way to test a hypothesis or confirm the results of a prior investigation.

• It isolates a single variable by controlling all other variables that may affect the outcome of the investigation.

Why is it important to use controlled variables in a scientific experiment?

• To make sure you get the correct results.

• To see how they affect the dependent variable.

• To make sure they don’t affect the outcome.

• To see how they are affected by the independent variable.

How does a scientist know if he/she has run enough trials in an investigation?

• Three trials is the standard expectation

• Ten trials usually gives reliable data

• When the data is consistent and predictable

• When they get the answer they expected

What has to happen for a scientific theory to become a scientific law?

• It has to be confirmed consistently and predictably through repetition and replication

• It must be proven beyond a reasonable doubt by the empirical evidence

• The overwhelming majority of scientists must form a consensus agreeing with it

• It will never become a scientific law because it has a different purpose

How are scientific theories related to scientific laws?

• Theories are used to explain laws

• Theories are less important than laws

• Theories are laws that haven’t been proven yet

• Theories don’t have as much evidence as laws

Which of these is considered a limitation of scientific models?

• Models can be cheaper to study

• Models can allow scientists to study the topic more safely

• Models can create misconceptions

• Models can simplify a complex idea

Alex is testing how the amount of sunlight given to sunflowers affects their growth rate. What is the INDEPENDENT variable in his experiment?

• the type of light

• the type of plant

• the growth rate

• the amount of light

Alex is testing how the amount of water given to sunflowers affects their growth rate. What is the DEPENDENT variable in his investigation?

• the type of water

• the amount of water

• the amount of sunlight

• the growth rate

Alex is testing how the amount of fertilizer affects the growth rate of sunflowers. Which of these would represent an example of repetition in Alex's experiment?

• Alex uses multiple sunflower plants for each amount of fertilizer that he tests

• Alex performs the same investigation using tulips instead of sunflowers

• Alex includes a sunflower plant that does not receive any fertilizer at all

• Samantha performs Alex's investigation using the same procedures

Alex is testing how the color of light affects the growth rate of sunflowers. Which of the following variables should be controlled (kept constant)?

• the color of light given to the sunflowers

• the growth rate of the sunflowers

• the amount of water given to the sunflowers

• all of these should be kept constant