Variables and Scientific Method

In Felix County, the population of slugs has tripled.  Laura, who lives in the area, heard that salt may work to exterminate them.  To test this, she will use different amounts of kosher salt on the species of slug Slime slimosis.  All the slugs will be 10 days old and will weigh 10 grams.  To make sure the slugs will die from their exposure to salt and not because of other variables she also decides to observe 5 slugs that will not be exposed to the salt.  What is the independent variable?

• Amount of slugs
• The species Slime slimosis
  
• Amount of food
• Amount of salt

In Felix County, the population of slugs has tripled.  Laura, who lives in the area, heard that salt may work to exterminate them.  To test this, she will use different amounts of kosher salt on the species of slug Slime slimosis.  All the slugs will be 10 days old and will weigh 10 grams.  To make sure the slugs will die from their exposure to salt and not because of other variables she also decides to observe 5 slugs that will not be exposed to the salt.  What is the dependent variable?

• Weight of the slugs
• Survival or death of the Slug
• The Environment
• Amount of Salt

Omar studied how far room temperature water would spurt out of a plastic milk carton when 3mm holes were punched at different heights from the bottom of the container.  Identify the independent/test variable.

• 3mm holes
• distance water traveled out of the carton
• different heights of holes in container
• ice water from Iceland

Mrs. Mello wanted to see how different types of music affected students’ pulse rates.  She played different types of music: rock, rap, R&B, alternative, pop, country, and classical music.  What constant should be considered when doing this experiment?

• types of music
• amount of time the music was played
• using a different student for each type of music
  
• use all dead people

Tatiana was investigating how much time it took Hayden to react to different sounds.  Identify the independent/test variable.

• how fast Hayden reacted
• how much time it took Hayden to react
  
• playing the trumpet over and over
• different sounds

Tracy wanted to see how high an ice cube would float in different temperatures of water.  Identify the independent/test variable

• height of ice cube
• temperature the ice cube was at its highest height
• size of ice cube
• temperature of water

Nick wanted to see how high an ice cube would float in different temperatures of water.  Identify the dependent/outcome variable.

• height of ice cube when floating
• amount of water
• temperature of water
• size of ice cube

Which of the following is a synonym (words that have the same meaning) of the dependent/outcome variable?

• responding
  
• cause
  
• manipulating
• investigating

Which of the following is a synonym (words that have the same meaning) of the independent variable?

• test
• outcome
• responding
  
• concluding

How many independent variables should a scientist have in a controlled experiment?

• one
  
• three
  
• depends on the experiment
• depends on the scientist