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  • 1.  
  • 2.  
  • 3.
    • Before we can perform an experiment designed to answer this question, we must determine the independent and dependent variable.
    • For an experiment to have valid results, there can be only one independent variable.
    THIS IS IMPORTANT!
  • 4.
    • The independent variable is the variable that you, as the scientist, will vary to observe the effect
    • The independent variable is sometimes called the manipulated variable because it is the variable the scientist manipulates.
  • 5.
    • The dependent variable is the variable that you, as the scientist, will measure and record – it’s the data of the experiment
    • The dependent variable is sometimes called the “ responding ” variable because it is the variable that responds to the independent (or manipulated) variable
  • 6.
    • To determine the independent and dependent variable, identify the two things that will (might) change:
      • lack of sleep
      • weight of an individual
  • 7.
    • Once you know the two things that are (or might be) changing, arrange them in a question like this:
    • In this experiment, does the lack of sleep depend on weight gain?
    • OR
    • Does weight gain depend on lack of sleep?
    • The variable that depends on the other is the dependent variable.
  • 8.
    • A lack of sleep depends on weight gain?
    • OR
    • that weight gain depends on a lack of sleep ?
    • Weight gain depends on the lack of sleep so weight gain is the dependent variable.
  • 9.
    • It’s important to understand that you don’t yet have to know if weight gain depends on a lack of sleep – you just need to identify which variable you will be manipulating and which variable will respond to your manipulations.
  • 10.
    • What effect does being raised on a fish farm have on a salmon’s length?
    • What two factors are being studied?
    • salmon’s length
    • raised on a fish farm
  • 11.
    • What effect does being raised on a fish farm have on a salmon’s length?
    • Does being raised on a fish farm depend on the salmon’s length?
    • OR
    • Does the length of the salmon depend on being raised on a fish farm?
  • 12.
    • The length of the salmon depends on being raised on a fish farm
    • Independent Variable?
      • raised on fish farm
    • Dependent Variable?
      • length of salmon
  • 13.
    • On the following slides, write down the research question in your notes and then discuss with your partner what you believe the two factors that will (might) change are.
    • After you agree on the two factors, see if you can agree on which one is the independent variable and which one is the dependent variable.
  • 14.
    • Two factors being studied?
      • presence of music
      • number of tomatoes grown
  • 15.
    • presence of music
    • number of tomatoes
    dependent variable?
  • 16.
    • Two factors being studied?
      • frequency of exercise
      • number of infections with cold virus
  • 17.
    • exercise
    • number of colds over a specified time period
    dependent variable?
  • 18.
    • Two factors being studied?
      • use of cell phones while driving
      • number of automobile accidents involved in
  • 19.
    • use of cell phones while driving
    • number of auto accidents involved in
    dependent variable?
  • 20.
    • Once you know the independent and dependent variables, writing a hypothesis statement is easy!
    • A hypothesis simply combines the independent and dependent variables into a prediction statement.
  • 21.
    • Research Question: What effect does salt have on the boiling point of water?
    • Independent Variable:
    • adding salt
    • Dependent Variable:
    • boiling point of water
  • 22.
    • IV: adding salt to H 2 O DV: boiling temp
    • A good hypothesis statement is an “if” “then” statement.
    • If salt is added to water, then the boiling point of water will increase.
  • 23.
    • If salt is added to water, then the boiling point of water will increase.
    • The independent variable is the “if” part of the hypothesis and the dependent variable is the “then” part.
  • 24.
    • a statement that predicts something
    • testable
    • an “if” “then” statement
  • 25.
    • a question
    • a statement that has words in it like
      • maybe
      • probably
      • might
  • 26.
    • A hypothesis might also have a “because” section
    • In the prior example, the “because” would sound like this:
    • If salt is added to water, then the boiling point will increase because salt is an ionic compound and ionic compounds are known to elevate boiling points.
  • 27.
    • What is the effect of wing size on the falling speed of a rotocopter?
    • What are the two factors?
      • wing size
      • falling speed
    • Which factor is the independent variable? Dependent variable?
      • ind v: wing size dep v: falling speed
  • 28.
      • ind v: wing size dep v: falling speed
    • If the wing size is increased, then the falling speed of the rotocopter will decrease.
    • or
    • If the wing size is increased, then the falling speed of the rotocopter will decrease because increased wing size will result in increased air resistance.
  • 29.
    • What effect does sandpaper have on a block of wood’s sliding velocity?
    • Two factors?
      • sandpaper
      • sliding velocity
    • Ind V and Dep V?
      • IV: sandpaper DV: sliding velocity
  • 30.
      • IV: sandpaper DV: sliding velocity
      • If a block of wood is pulled on a sandpaper surface instead of a wooden surface, then the sliding velocity will decrease.
      • or
      • If a block of wood is pulled on a sandpaper surface instead of a wooden surface, then the sliding velocity will decrease because the force of friction of the sandpaper will be greater.
  • 31.
    • THE FINE PRINT
    • © Jan Parker, 2009 – for purchaser’s classroom use only; please do not distribute. If other teachers in your school like what they see, send them to my website http://www.thesciencevault.com or to my web store http://www.teacherspayteachers.com/Store/Jan-Parker 
    • If you put your classroom materials on a server for your students, please post this presentation in pdf form. Thanks!