SCIENTIFIC SCIENTIFIC METHODMETHOD

The Scientific Method involves a series of steps that are used to investigate a natural occurrence.

Steps in the Scientific Steps in the Scientific MethodMethod

ObservationObservation HypothesisHypothesis ExperimentExperiment ConclusionConclusion

ObservationsObservations

Gathered Gathered through your through your

sensessenses Identifying Identifying

and clearly and clearly defining the defining the

problemproblem

ObservationsObservations

An An exampleexample of of an observationan observation

might be might be noticing that noticing that

many many salamanders salamanders near a pond near a pond

have curved, not have curved, not straight, tailsstraight, tails

HypothesisHypothesis

A suggested A suggested solution to the solution to the problem.problem.

Must be Must be testabletestable Sometimes Sometimes

written as written as If…If…Then…Then… statementsstatements

PredictsPredicts an an outcomeoutcome

HypothesisHypothesis

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

ExperimentExperiment A procedure to A procedure to testtest

the hypothesis.the hypothesis. Conducting Conducting

controlled attempts controlled attempts to test one or more to test one or more

hypotheseshypotheses Includes Includes recording recording

and analyzing and analyzing resultsresults

ExperimentExperiment

VariableVariable – – factor in the factor in the experiment experiment that is being that is being

testedtested

ExperimentExperiment

A good or A good or “valid” “valid”

experiment experiment will only will only

have have ONE ONE variable!variable!

CONTROLS AND CONTROLS AND VARIABLESVARIABLES

Scientific Experiments Scientific Experiments Follow RulesFollow Rules

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

The Control The Control Variable/GroupVariable/Group The experimenter makes a The experimenter makes a

special effort to keep special effort to keep other other factors constantfactors constant so that so that they will not effect the they will not effect the outcome.outcome.

Those factors are called Those factors are called control/constant variables.control/constant variables.

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

Controls are NOT being tested

Controls are used for COMPARISON

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.

Example of Controls & Example of Controls & VariablesVariables

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.

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

Varying the route is the Varying the route is the independent variableindependent variable

The time it takes is the The time it takes is the dependent variabledependent variable

Keeping the same walker Keeping the same walker throughout makes the throughout makes the walker a walker a control variable.control variable.

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

VALID EXPERIMENTSVALID EXPERIMENTS

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

Two groups are required --- the control & experimental groups

There should be only one variable

DataData Results of

the experiment

May be quantitative (numbers) or qualitative

DataData Must be

organized Can be

organized into charts, tables, or graphs

ConclusionConclusion The answer to the

hypothesis based on the data obtained from the experiment

Formulating a generalization about the results, which may accept, reject or modify a hypothesis

RetestRetest

In order to verify the results,

experiments must be retested.

Sample ProblemsLet's say I have a problem: My car won't start. How would I use the

scientific method to solve this problem?  

Problem: My car won’t start. I want it to start. Hypothesis: If I put gas in my car, it will start. Materials: 5 gallon gas can, 5 gallons gasoline, money to buy

gasoline, a ride to the gas station Experiment: First, I will call my friend Bill and ask for a ride to the

gas station. I will take the five gallon gas can and fill it with five gallons of gasoline at the pump. After paying the gas station owner for the gasoline, I will get a ride back to my car and put the gasoline in the tank. Once the gasoline is in the tank, I will attempt to restart the car.

Results: The car started on the first try. Conclusion: When I put gas in my car, it started.

Mr. Smithers believes 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, Mr. Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.

The control group of this example is Group B, because they are not given the special juice. They are just there for explaining the results. The experimental group of this example is Group A, because they are given the special juice. This is the factor that you are experimenting on.

Question Independent Variable (What I Change)

Dependent Variables (What I Observe)

Controlled Variables (What I keep the same)

Who listens to music the most: teenagers or their parents?

The groups receiving the survey: teenagers or parents

The amount of time that each person listens to music per day measured in hours

Ask the question in exactly the same way to each individual

How fast does a candle burn?

Time measured in minutes

Height of candle measured in centimeters at regular intervals of time (for example, every five minutes)

Use same type of candle for every test

Wind--make sure there is none

REVIEWREVIEW

Solving a ProblemSolving a Problem1) Identify a Problem2) State Observations

about the problem3) Form a Hypothesis

about the problem (if…then…)

4) Design an Experiment to test the hypothesis

5) Collect Data6) Form a Conclusion7) Retest