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Scientific Method

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**Steps in the Scientific Method**

Observation State the Problem Hypothesis Experiment Data Collection Conclusion Retest

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**Observations Gathered through your senses**

A scientist notices something in their natural world

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Observations An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

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**Hypothesis A suggested solution to the problem. Must be testable**

Sometimes written as If…Then… statements Predicts an outcome

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Hypothesis An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live.

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**A procedure to test the hypothesis.**

Experiment A procedure to test the hypothesis.

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**Variable – factor in the experiment that is being tested**

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**A good or “valid” experiment will only have ONE variable!**

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**Controls and Variables**

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**Scientific Experiments Follow Rules**

An experimenter changes one factor and observes or measures what happens.

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The Control Variable The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. (ex: length of time, temperature, locations) Those factors are called control variables.

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**What is the Purpose of a Control?**

Controls are NOT being tested Controls are used for COMPARISON

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Other Variables The factor that is changed is known as the independent variable. The factor that is measured or observed is called the dependent variable.

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**Example of Controls & Variables**

For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

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**What are the Variables in Your Experiment?**

Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.

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**1. Control Group 2. Independent (Manipulated) Variable 3**

1. Control Group 2. Independent (Manipulated) Variable 3. Dependent (Responding) Variable 4. What should Smithers' conclusion be? 5. How could this experiment be improved? Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.

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**One more thing… it is best to make several trials with each independent variable.**

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Valid Experiments

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**Remember: To be a Valid Experiment:**

Two groups are required --- the control & experimental groups There should be only one variable Control Group: used as a comparison; receives the normal condition Experimental Group: receives additional or alternate treatment

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**Data Results of the experiment**

May be quantitative (numbers) or qualitative

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Data Must be organized Can be organized into charts, tables, or graphs

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**Types of Graphs Bar Graph- used to compare sets of data**

Pie Graph-based upon a whole or % Line Graph- follows a trend or period of time

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**Graphing in Science Data in correct location**

Graph ✔ List Data in correct location Axes labeled with units (cm, L, s, kg, etc.) Axes evenly spaced out Accurate title Correct graph type

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Graphs

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Conclusion The answer to the hypothesis based on the data obtained from the experiment

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**Retest In order to verify the results, experiments must be retested.**

Should be complete at least 3 times to obtain average data.

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**Solving a Problem 1)Identify a Problem**

2) State Observations about the problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest

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