DNMQ #19: Controlled Experiments & Variables (Fall 2023)

Which step of the scientific method/ experimental design is represented by the following statement: Stephen predicted that seeds would start to grow faster if an electric current traveled through the soil in which they were planted.

• recognize a problem
• test the hypothesis with an experiment
• form a hypothesis
• draw conclusions  

How many independent variables should you have in an experiment?

• two

• as many as possible

• four

• one

What is an independent variable?

• What a scientist changes in an experiment to test their hypothesis

• What scientist measure to see if it responded to a change

• What happens when you do an experiment

• What you keep the same throughout all experimental groups

What is an dependent variable?

• What a scientist changes in an experiment to test their hypothesis

• What scientist measure to see if it responded to a change

• What happens when you do an experiment

• What you keep the same throughout all experimental groups

Conditions that are the SAME between the control and experimental groups

• Independent Variable

• Constants

• Dependent Variable

• Data

Does temperature affect heart rate in daphnia? Name the dependent variable.

• Temperature

• Type of organism

• Heart Rate

• Number of daphnia in each group

Carmen conducted an experiment to determine if listening to different types of music would affect a person’s pulse. Her hypothesis was that pulse rate would change with different types of music. Each person listened to seven different selections of music for 30 seconds each. Each person’s pulse was taken before the music and then after each 30-second interval of music. The pulses were taken again after the music selections were completed. Based on her experiment, Carmen concluded that a person’s pulse rate changed when the person listened to different types of music.  Which component is missing from Carmen’s experiment?

• a question
• a hypothesis
• a control group
• a description of the experiment

An experiment was carried out to determine whether drinking caffeinated soda increases pulse rate. The pulse rates of two groups of people at rest were measured. Group A was then given caffeinated soda and group B was given caffeine-free soda. One hour after drinking the soda, the pulse rates were measured. The participants in the experiment were all the same age, and they were all given the same amount of soda. The dependent variable in this experiment is the

• type of soda given to each group
• amount of soda given to each group
•  pulse rate of each group
• age of participants in each group

This scientific variable is graphed on the x-axis. 

• Dependent
• Control Group
• Independent
• Constant

In a controlled scientific experiment, a scientist...

• alters the outcome variable (dependent variable) and observes the effects on the test variable (independent variable).

• alters one test variable (independent variable) and observes the effects on other test variables (independent variables).

• alters the test variable (independent variable) and observes the effects on the outcome variable (dependent variable).

• 
  alters one outcome variable (dependent variable) and observes the effects on other outcome variable (dependent variables).