Scientific MethodScientific Method

systematic approach toward answering scientific questions

Steps in the Scientific Steps in the Scientific MethodMethod

• ObservationObservation• Question/Question/

ProblemProblem• HypothesisHypothesis• ExperimentExperiment• Data CollectionData Collection• ConclusionConclusion• RetestRetest

ObservationsObservations

• Gathered Gathered through your through your

sensessenses• A scientist A scientist

notices notices something in something in their their natural natural

worldworld

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

Observation leads to a Observation leads to a Question?Question?

HypothesisHypothesis

• A suggested A suggested solution to the solution to the question/problemquestion/problem..

• Must be Must be testabletestable• PredictsPredicts an an

outcomeoutcome• Sometimes Sometimes

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

ExperimentExperiment

•A A procedure procedure to to testtest the the hypothesishypothesis

..

ExperimentExperiment

Experimental Experimental VariableVariable – –

factor in the factor in the experiment experiment that is being that is being

testedtested

ExperimentExperiment

A A controlled controlled experiment experiment (“fair test”) (“fair test”)

will only will only have have ONE ONE

experimentaexperimental variable!l variable!

Scientific Experiments Scientific Experiments Follow RulesFollow Rules

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

•The experimenter makes The experimenter makes a special effort to keep a special effort to keep other factors constantother factors constant so so that they will not effect that they will not effect the outcome.the outcome.

• Those factors are called Those factors are called controlled variables.controlled variables.

What is a What is a ControlControl??

•used for comparison•controls are NOT being tested•the non-experimental or normal group

Eg. In a fertilizer test, plants treated with no fertilizer or the regular fertilizer are control group

RememberRemember, to be a , to be a Controlled Experiment Controlled Experiment

(aka “fair test”):(aka “fair test”):•Two groups are required

--- the control & experimental groups

•There should be only one experimental variable tested

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 walker a throughout makes the walker a controlled variable controlled variable

• Worksheet “SCIENTIFIC METHOD: Controls and Variables”

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

RetestRetest

In order to verify the results,

experiments must be retested.

ReviewReview

Solving a ProblemSolving a Problem

1)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 and analyze Data

6) Form a Conclusion7) Retest