Responsible Experimental Responsible Experimental DesignDesign

The Scientific MethodThe Scientific Method

STEP 1: Ask a Scientific STEP 1: Ask a Scientific Question!Question!

• The The Scientific methodScientific method is a series of steps is a series of steps followed to solve problems.followed to solve problems.

• To start the process of investigation you have To start the process of investigation you have to be curious about something. A scientific to be curious about something. A scientific question is a very specific question that can be question is a very specific question that can be answered through observation, measurement, answered through observation, measurement, testing, or analysis.testing, or analysis.• ObservationObservation – the process of obtaining – the process of obtaining

information by using the senses.information by using the senses.• Questioning a promotional claim can be a good Questioning a promotional claim can be a good

starting point.starting point.• Promotional claimPromotional claim – a statement used to sell – a statement used to sell

a product, service, or concept.a product, service, or concept.

STEP 2: Form a Hypothesis!STEP 2: Form a Hypothesis!• A A hypothesishypothesis is an educated guess that answers your is an educated guess that answers your

scientific question. It is based on inference, informed scientific question. It is based on inference, informed decision, logic, research, and experience.decision, logic, research, and experience.• InferenceInference – a prediction based on experience and – a prediction based on experience and

knowledge rather than on direct observation.knowledge rather than on direct observation.• Informed decisionsInformed decisions – conclusion that considers the – conclusion that considers the

data that are relevant to making a particular choice.data that are relevant to making a particular choice.• A hypothesis should be something that can be tested A hypothesis should be something that can be tested

through an experiment.through an experiment.• A A controlled experimentcontrolled experiment is a procedure designed to is a procedure designed to

test a hypothesis that includes a control group and test a hypothesis that includes a control group and experimental group.experimental group.

STEP 3: Design an Experiment!STEP 3: Design an Experiment!• Determine your Determine your variablesvariables - factors that can - factors that can

impact the results of the experiment.impact the results of the experiment.• There are two type of variables: Independent There are two type of variables: Independent

and dependent.and dependent.• Independent variablesIndependent variables are changed or are changed or

controlled by the experimenter.controlled by the experimenter.• Dependent variablesDependent variables are responses or are responses or

results that you get after changing the results that you get after changing the independent variable.independent variable.

• Set up the experimental groups.Set up the experimental groups.• Control groupControl group – represents what would happen – represents what would happen

if the independent variable was not if the independent variable was not manipulated.manipulated.

• Experimental group – the only thing different Experimental group – the only thing different than the control group is the changes in the than the control group is the changes in the independent variable.independent variable.

STEP 3: Design an Experiment!STEP 3: Design an Experiment!

• Experimental design must be guided by Experimental design must be guided by ethics. ethics. EthicsEthics are standards of conduct are standards of conduct and moral judgment. An example would and moral judgment. An example would be conducting research in way that be conducting research in way that reduces risks to people, animals, and reduces risks to people, animals, and the environment. Scientists must act the environment. Scientists must act responsibly and with integrity.responsibly and with integrity.

STEP 3: Design an Experiment!STEP 3: Design an Experiment!

• You need to have an accurate, specific You need to have an accurate, specific record of all of the steps of the record of all of the steps of the experiment.experiment.

• This step-by-step plan is called the This step-by-step plan is called the procedureprocedure..

• Your procedure should be clear enough Your procedure should be clear enough that another scientist or science student that another scientist or science student could repeat the experiment and verify could repeat the experiment and verify your results.your results.

Step 4: Analyze the Data.Step 4: Analyze the Data.

• Data Data (this is plural) are information (this is plural) are information collected through scientific research.collected through scientific research.

• Data can be…Data can be…• Notes,Notes,• Drawings,Drawings,• Measurements, orMeasurements, or• ObservationsObservations

Step 4: Analyze the Data.Step 4: Analyze the Data.

• Data collected in numerical form are Data collected in numerical form are called called quantitative dataquantitative data..• Quantitative data can be analyzed by Quantitative data can be analyzed by

knowing the range of the data and by knowing the range of the data and by finding the mean, median, and mode finding the mean, median, and mode of the data.of the data.

• Qualitative dataQualitative data describe an object in describe an object in words rather than in numbers.words rather than in numbers.

Step 5: Form a Conclusion!Step 5: Form a Conclusion!

• Your Your conclusionconclusion should explain the should explain the results of the experiment and show results of the experiment and show any relationships that exist between any relationships that exist between the variables. Your conclusion the variables. Your conclusion should also state whether the data should also state whether the data support your hypothesis or not.support your hypothesis or not.

• Conclusions must be Conclusions must be objectiveobjective – – based on facts and free of bias. based on facts and free of bias. BiasBias is a personal prejudice or slanted is a personal prejudice or slanted point of view.point of view.

Good experiments include Good experiments include multiple trials!multiple trials!

• Each time you modify or conduct the experiment the Each time you modify or conduct the experiment the new experiment is called a new experiment is called a trialtrial. .

• For a hypothesis to be accepted many trials must be For a hypothesis to be accepted many trials must be conducted to make sure the results turn out the same conducted to make sure the results turn out the same each time!! This helps to increase the accuracy, each time!! This helps to increase the accuracy, reliability, and validity of the experiment.reliability, and validity of the experiment.• Accuracy Accuracy refers to the correctness of a measurement refers to the correctness of a measurement

or conclusion!!or conclusion!!• PrecisionPrecision describes the exactness of the process. describes the exactness of the process.

Your procedure should be able to be replicated! Your procedure should be able to be replicated! • ReliabilityReliability refers to the level of trust you can place in refers to the level of trust you can place in

information.information.• Experiments with Experiments with validityvalidity are known to be based on are known to be based on

facts and truth.facts and truth.

Theory vs. LawTheory vs. Law• After many trials, hypotheses may be After many trials, hypotheses may be

accepted as theory. A accepted as theory. A theorytheory is a tested is a tested explanation for hypotheses and explanation for hypotheses and observations.observations.

• Laws do not explain how or why Laws do not explain how or why something happens. A scientific something happens. A scientific lawlaw summarizes repeated observations. summarizes repeated observations. • For example: the law of gravity tells us that For example: the law of gravity tells us that

every time we drop an object it will fall. The every time we drop an object it will fall. The law does not explain how or why it will fall, law does not explain how or why it will fall, just that it will fall.just that it will fall.