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V ARIABLES Independent vs. Dependent

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9/8V ARIABLES & H YPOTHESES IQ: Jane did an investigation to see the effect of temperature on the growth of mold on a slice of bread. She left one slice in the fridge and another on her kitchen counter. What is independent var. and the dependent variable in this experiment?

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V ARIABLE Variable- Something that is changed in an experiment. In scientific experiments there are two variables- One that you control and one that is the result.

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I NDEPENDENT VARIABLE - T HE C AUSE The one thing that is changed by the experimenter In a graph it is on the x- axis(along the bottom) Ex. The amount of explosive chemicals inside a firecracker.

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D EPENDENT V ARIABLE The result of the experiment What is measured This depends on what you changed- the IV. On a graph, it is on the y- axis(along the vertical side) Example: the loudness of a firecracker (d.v.) depends on the amount of explosive chemicals used (i.v).

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G RAPHING V ARIABLES

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Direct RelationshipInverse relationship

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T HE IV CAUSES THE DV TO CHANGE 1. The temp. of the water was measured at different depths of the lake. Two things were changed in this statement. The first was the depths and the second was the temperature. Plug these into the bolded statement: The depth causes the temp to change. IV: depth DV: temp

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2. The amount of time you study will make a positive difference on your next test score. Two things are changed: 1. Time spent studying 2. Score on next test. The ____________causes _________ to change. IV: ____________ DV: _____________

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C ONTROL V ARIABLE A Control variable is anything else that could influence the dep. var. Control variables must be carefully monitored and kept equal/same in the experiment or they could mess up the results by making your results false or unreliable. For example, when testing to see if a plant that is given fertilizer grows taller than one without: What is the IV? :_________What is the DV?:_________ What other variables could also affect the growth of the plants? ___________________. These are the control variables and should be kept the same for both plants.

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Control setup/group- Part of the experiment that does NOT get any special treatment, IV is not changed or introduced.

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D EVELOPING H YPOTHESES

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Problem has been stated Question Research (Using your five senses and prior knowledge) A Hypothesis is formulated

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W HAT IS A H YPOTHESIS A hypothesis is an inference (based on observations and prior knowledge) about what will happen in an experiment. The hypothesis should tell what you will do or how the IV will change, predict what the answer to your question will be or how the DV will be affected, and give reasons why.

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F ORMAT FOR WRITING A HYPOTHESIS Most of the time a hypothesis is written like this: "If _____[I do this] _____, then _____[this]_____ will happen, because ________ [mention your research or prior knowledge]" (Fill in the blanks with the appropriate information from your own experiment.) If I press harder on the gas pedal, then I will get a ticket because I will go past the speed limit. Your hypothesis should be something that you can actually test, what's called a testable hypothesis. In other words, you need to be able to measure both "what you do" and "what will happen."

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M ORE E XAMPLES OF H YPOTHESES "If I open the faucet [faucet opening size is the independent variable], then it will increase the flow of water [flow of water is the dependent variable], because more water can come out at a time. "Raising the temperature of a cup of water [temp. is the IV) will increase the amount of sugar that dissolves [amt. of sugar is the DV], because the molecules will move faster." "If a plant receives fertilizer [having fertilizer is the independent variable], then it will grow to be bigger than a plant that does not receive fertilizer [plant size is the dependent variable], because fertilizer adds more nutrients to the soil."

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OQ: Determine IV and DV, and create a hypothesis for the following question: How will my overall class grade be affected by my score on Fridays test?

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9/9 G UMMY B EAR LAB IQ: A student is doing an investigation for the following question: What is the effect of rainy weather on school attendance? IV:_____, DV:________ Hypothesis: Type of relationship between variables:________ (direct or inverse)

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ACC Design a controlled experiment with at least 2 experimental setups where a gummy bear is left in a liquid overnight. Decide on your independent (what will you change or expose the gummy bear to) and dependent variables (which characteristic/s will you observe to see if they get affected), create a question and start your lab report. You may work individually or with a partner. Materials available: Rubbing alcohol, hydrogen peroxide, water, salt, vinegar, cup, gummy bears, ruler, triple beam balance. You should be done through your data table (show me) to be able to start the lab.

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G UMMY B EAR LAB Question : How is the length and ________ of a gummy bear affected if it is soaked in water overnight? Research: (Record observations and prior knowledge) Hypothesis : If ____________, then its length will ________ and its _________ (mass, smell, color, texture) will _______, because _____________.

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Procedures: 1. Measure and record length of gummy bear. 2. ___________ 3. Fill cup with water about 3/4 full. 4. __________________ 5. _________________

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D ATA T ABLE DayLength?

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9/10 P.16G UMMY B EAR L AB CONT D IQ: Which type of graph would be best suited for the data you collect from the gummy bear lab?

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Create a graph for your data. Conclusion: Repeat your results with more details/comparisons. Was your hypothesis supported or not? What inferences can you make from your results or what did you learn from your experiment? What are some questions you have or how would you like to do this experiment differently in the future?

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OQ: List at least 3 control variables in the gummy bear lab.

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C REATE A H YPOTHESIS FOR EACH OF THE FOLLOWING QUESTIONS : Which textbook is heavier, Math or Geography? Which city is more populated, Seattle or Las Vegas? OQ: Create a question given the following 2 variables: IV: Time spent exercising. DV: Heart health