Ind and Dep variables plus hypothesis

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Ind and Dep variables plus hypothesis

  1. 1. 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!
  2. 2. 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.
  3. 3. 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
  4. 4. To determine the independent and dependent variable, identify the two things that will (might) change: lack of sleep weight of an individual
  5. 5. 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.
  6. 6. 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.
  7. 7. 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.
  8. 8. 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
  9. 9. 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?
  10. 10. The length of the salmon depends on being raised on a fish farm Independent Variable? raised on fish farm Dependent Variable? length of salmon
  11. 11. 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.
  12. 12. Two factors being studied? presence of music number of tomatoes grown
  13. 13. presence of music number of tomatoes dependent variable?
  14. 14. Two factors being studied? frequency of exercise number of infections with cold virus
  15. 15. exercise number of colds over a specified time period dependent variable?
  16. 16. Two factors being studied? use of cell phones while driving number of automobile accidents involved in
  17. 17. use of cell phones while driving number of auto accidents involved in dependent variable?
  18. 18. 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.
  19. 19. Research Question: What effect does salt have on the boiling point of water? Independent Variable: adding salt Dependent Variable: boiling point of water
  20. 20. IV: adding salt to H2ODV: 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.
  21. 21. 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.
  22. 22. a statement that predicts something testable an “if” “then” statement
  23. 23. a question a statement that has words in it like maybe probably might
  24. 24. 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.
  25. 25. 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
  26. 26. 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.
  27. 27. 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
  28. 28. 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.
  29. 29.  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!

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