Variables lecture
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The document discusses the key concepts of variables in scientific experiments. It defines different types of variables - independent, dependent, and controlled variables. The independent variable is the one that is deliberately changed by the scientist. The dependent variable is the one being measured to determine the effect of changes to the independent variable. Controlled variables are other factors that are kept the same to ensure the experiment is a fair test of only the independent variable. Good experiments clearly define each type of variable to help establish cause-and-effect relationships.
Variables lecture
- 1. VVaarriiaabblleess 1 VARIABLE |ˈVE(Ə)RĒƏBƏL| AADDJJEECCTTIIVVEE • NOT CONSISTENT OR HAVING A FIXED PATTERN; LIABLE TO CHANGE. • ABLE TO BE CHANGED OR ADAPTED : THE DRILL HAS VARIABLE SPEED. NNOOUUNN • AN ELEMENT, FEATURE, OR FACTOR THAT IS LIABLE TO VARY OR CHANGE.
- 2. Keeping Things Fair 2 It is important for an experiment to be a ffaaiirr tteesstt. To insure an experiment is a fair test, you must change only oonnee ffaaccttoorr aatt aa ttiimmee while keeping all other conditions the ssaammee. Scientists use an experiment to search for ccaauussee aanndd eeffffeecctt relationships in nature. Experiments are designed so changes to one item cause something else to vary in a pprreeddiiccttaabbllee way.
- 3. Variables 3 These changing quantities are called variables. A variable is any Factor Trait or Condition existing in differing amounts or types.
- 4. Variables 4 An experiment usually has three kinds of variables: 11.. IInnddeeppeennddeenntt 22.. DDeeppeennddeenntt 33.. CCoonnttrroolllleedd
- 5. Independent Variable 5 Is one variable changed by a sscciieennttiisstt. To insure a fair test, a good experiment has oonnllyy oonnee independent variable. As the scientist changes the independent variable, he or she oobbsseerrvveess what happens. There should be oonnllyy oonnee independent variable for any valid experiment.
- 6. Dependent Variable 6 The scientist focuses his or her observations on the dependent variable to see hhooww iitt rreessppoonnddss to the change made to the independent variable. The nneeww vvaalluuee of the dependent variable is caused by and depends on the value of the independent variable. There can be mmoorree tthhaann oonnee dependent variable.
- 7. Controlled Variables 7 Experiments also have ccoonnttrroolllleedd variables. Controlled variables are quantities rreemmaaiinniinngg constant They must be oobbsseerrvveedd as carefully as the dependent variables.
- 8. Variables are measured 8 In a good experiment, the scientist must be able to mmeeaassuurree the values for each variable.
- 9. More to Think About 9 The independent variable is the variable that is varied or mmaanniippuullaatteedd by the researcher The dependent variable is the rreessppoonnssee that is mmeeaassuurreedd. An independent variable is the pprreessuummeedd ccaauussee, whereas the dependent variable is the pprreessuummeedd eeffffeecctt. The dependent variable provides the ddaattaa you collect.
- 10. Types of Variables Remember these guides: Question Independent Variable 10 Dependent Variables Controlled Variables What I change What I observe What I keep the same
- 11. Types of Variables Question Independent Variable Dependent Variables Controlled Variables What I change What I observe What I keep the same How much water flows through a faucet at different openings? Water faucet opening (closed, half open, fully open) Amount of water flowing measured in liters per minute • The Faucet •Water pressure, or how much the water is "pushing" "Different water pressure might also cause different amounts of water to flow and different faucets may behave differently, so to insure a fair test I want to keep the water pressure and the faucet the same for each faucet opening that I test.” 11
- 12. Types of Variables Question Independent Variable Dependent Variables Controlled Variables What I change What I observe What I keep the same Does fertilizer make a plant grow bigger? Amount of fertilizer measured in grams. •Growth of the plant measured by its height. •Growth of the plant measured by the number of leaves. •See Measuring Plant Growth for more ways to measure plant growth . •Same size pot for each plant. •Same type of plant in each pot. •Same type and amount of soil in each pot. •Same amount of water and light. •Make measurements of growth for each plant at the same time. "The many variables above can each change how fast a plant grows, so to insure a fair test of the fertilizer, each of them must be kept the same for every pot." 12
- 13. Outcomes & Results 13 The outcome describes the rreessuullttss of your experiment. Henry and Eliza conducted an experiment using plant fertilizer. They added different amounts of fertilizer to seven pots of bean sprouts. The pots were the same size and had the same type and amount of soil. They were given the same amount of seeds, light, and water. To find out how the fertilizer affected the growth of the sprouts, Henry and Eliza calculated the average height of the bean sprouts in each pot. Here are the factors in their experiment:
- 14. Outcomes & Results Changed variable: ?? Controlled factors: 11.. ?? 22.. ?? 33.. ?? 44.. ?? 55.. ?? Outcome: ?? 14
- 15. Outcomes & Results 15 Changed variable: aammoouunntt ooff ffeerrttiilliizzeerr Controlled factors: 11.. ssiizzee ooff ppoottss 22.. aammoouunntt ooff lliigghhtt 33.. aammoouunntt ooff wwaatteerr 44.. aammoouunntt ooff ssooiill 55.. nnuummbbeerr ooff sseeeeddss Outcome: aavveerraaggee hheeiigghhtt ooff bbeeaann sspprroouuttss