Independent vs. Dependent Variables Independent vs. Dependent

9/14 p.12 Variables and Hypotheses IQ: On yellow half sheet

Variables & Hypotheses 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?

Variable 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.

Independent variable- “The Cause” 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.

Dependent Variable 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).

Graphing Variables

Direct Relationship-As X increases Y increases Inverse relationship- As X inc Y dec

The 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

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: _____________

Control Variable 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.

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

Developing Hypotheses

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

What is a Hypothesis 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.

Format 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."

More Examples of Hypotheses "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."

p. 12 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 Friday’s test?

Practice: In the scenario below, identify the following components of an experiment. Underline and number them on the paragraph. Independent variable Dependent variable Hypothesis Control setup Control variables/Constants Scenario  Jack wanted to test which brand of car wax was most effective. He tested four brands (A-D) of wax. He proposed that drops of water would spread the most on the wax that worked the best as the waxed surface would be more slippery. He cleaned the hood of his car and removed the old wax. He measured five equal sections on the hood of the car. Each of the waxes was used to cover a section, and one section was left un-waxed. An equal amount of wax, the same type of rag, and equal buffing were used. Ten drops of water were placed on each square, and the diameter of each drop was measured (cm). 

Practice: Find the error/s in the following experiment-   JoAnna read that certain perfume esters would agitate bees.  Because perfume formulas are secret, she decided to determine whether the unknown Ester X was present in four different perfumes by observing the bees’ behavior.  She placed a saucer containing 10 mL of the first perfume 3 m from the hive.  She recorded the time required for the bees to emerge and made observations on their behavior.  After  30-minute recovery periods, she tested the second, third, and fourth perfumes in 10 mL quantities.  All experiments were conducted on the same day.

9/15 p. 14 Gummy Bear 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)

Gummy Bear Lab You will be seeing the effects of leaving a gummy bear in water overnight. You will be working with a partner. Make sure to label your cup before leaving today. What are some things/qualities you could observe in a gummy bear to see if it gets affected by water overnight? Decide on one to use as a dependent variable. Complete the lab sheet as you go. Place cup with gummy and water on counter after making sure you have your name on it. I will cover them after.

ACC Design a controlled experiment (need to control variables) 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 in groups of 2 to 3 people. Materials available: Rubbing alcohol, hydrogen peroxide, water, lemon juice, vinegar, cup (59 mL), gummy bears, ruler, triple beam balance, graduated cylinders (50 mL) You should be done through your data table (at least 1 person in group- show me) to be able to start the lab.

p. 15 Gummy Bear 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 __________________

Procedures: Measure and record length of gummy bear. Observe/measure ___________ of gummy bear and record. Fill cup with water about 3/4 full. ____________________________________________ ____________________________________________

Data Table Day Length (cm) ______________

Get a paper towel, find your gummy bear cups, dump out the water VERY CAREFULLY!!! Slide your gummy bears out of the cup onto the paper towel. Do final observations and record!

9/16 p.14 Gummy Bear Lab cont’d IQ: Which type of graph would be best suited for the data you collect from the gummy bear lab and why?

Acc: Fill in and complete data table On p. 15 Create a graph or graphs for your data. Use the sheet on p. 2 to decide which type of graph to draw. 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?

p. 14 9/16 OQ: List at least 3 control variables in the gummy bear lab.

Create a Hypothesis 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