Experimental DesignExperimental Designand the Scientific and the Scientific

MethodMethod

Life Savers LabLife Savers Lab

There isThere is NO SINGLE METHODNO SINGLE METHOD for doing science!!!!for doing science!!!!

However, science involves a series of However, science involves a series of common steps...common steps...

Steps of the Scientific MethodSteps of the Scientific Method

1. Make an 1. Make an ObservationObservation

Example:Example: • It takes students differing amounts of It takes students differing amounts of

times to eat a Life Savers.times to eat a Life Savers.

Steps of the Scientific MethodSteps of the Scientific Method

2. Ask a 2. Ask a QuestionQuestion

Examples:Examples:• Does flavor influence how long it Does flavor influence how long it

takes to eat a Life Savers?takes to eat a Life Savers?

• Does gender affect how long it Does gender affect how long it takes to eat a Life Savers?takes to eat a Life Savers?

Steps of the Scientific MethodSteps of the Scientific Method3. Form a 3. Form a HypothesisHypothesis and … and …

4. Make a 4. Make a PredictionPrediction HypothesisHypothesis:: A proposed explanation A proposed explanation

that answers your question.that answers your question.• This must be TESTABLE!This must be TESTABLE!• Statement: If_________, then_______Statement: If_________, then_______

PredictionPrediction:: A statement that A statement that forecasts what would happen if your forecasts what would happen if your hypothesis is true.hypothesis is true.

Steps of the Scientific MethodSteps of the Scientific Method

5. 5. TestTest your hypothesis your hypothesis

ExperimentExperiment:: An investigation that An investigation that tests your hypothesis under tests your hypothesis under controlled conditions. controlled conditions.

Experimental DesignExperimental Design: How you : How you set up your experiment. set up your experiment.

Experimental DesignExperimental Design Control GroupControl Group = = you use the you use the

control group data to compare to control group data to compare to your experimental group datayour experimental group data

Experimental GroupExperimental Group = the group = the group that is being tested onthat is being tested on

Experimental Design Cont.Experimental Design Cont. ConstantConstant = = Anything that stays the same during Anything that stays the same during

an experiment (ex: same flavor, same stop an experiment (ex: same flavor, same stop watch, etc)watch, etc)• Controlling your experiment ensures that Controlling your experiment ensures that extra extra

independent variables independent variables can’tcan’t sneak in and affect your sneak in and affect your datadata

Independent VariableIndependent Variable = = It It affectsaffects the the dependent variable. This is the variable that you dependent variable. This is the variable that you changechange. . • Ex: Color of lifesaver, Flavor of lifesaverEx: Color of lifesaver, Flavor of lifesaver

Dependent VariableDependent Variable = = It It dependsdepends on the on the independent variable. This is the variable you independent variable. This is the variable you measuremeasure. . • Ex: the length of time to consume a lifesaverEx: the length of time to consume a lifesaver

Experimental Design Cont.Experimental Design Cont. Let’s say you have 2 variables and you can’t tell which should be the Let’s say you have 2 variables and you can’t tell which should be the

dependent variable dependent variable and which should be the and which should be the independent variable independent variable

We know that the dependent variable depends on the independent We know that the dependent variable depends on the independent variablevariable

Put the variables into this sentence and see if it makes sense Put the variables into this sentence and see if it makes sense “______ “______ depends on ______”depends on ______”

Which sentence makes more sense?Which sentence makes more sense?

““TemperatureTemperature depends on the depends on the Number of SharksNumber of Sharks.”.”

““The The Number of SharksNumber of Sharks depends on depends on TemperatureTemperature.”.”

Temperature (C)Number of Sharks

15 22

18 18

20 16

Steps of the Scientific MethodSteps of the Scientific Method6. 6. Analyze DataAnalyze Data and and Draw ConclusionsDraw Conclusions Qualitative DataQualitative Data = = Deals with Deals with

descriptions. Observed, but not descriptions. Observed, but not measured.measured.• Ex: color changes to the lifesaver as you Ex: color changes to the lifesaver as you

consume itconsume it Quantitative DataQuantitative Data = =Deals with Deals with

numbers, can be measured numbers, can be measured • Ex: The number of seconds needed to Ex: The number of seconds needed to

consume a lifesaversconsume a lifesavers Hint: Think “N” for NUMBER!Hint: Think “N” for NUMBER!

The table surface is smoothThe table surface is smoothQualitativeQualitative

The peanut weighs 1.75 gThe peanut weighs 1.75 gQuantitativeQuantitative

The leaf is dark brownThe leaf is dark brownQualitativeQualitative

There are 15 flowers with white petals on themThere are 15 flowers with white petals on themQuantitativeQuantitative

Qualitative or Quantitative?Qualitative or Quantitative?(pay attention but you don’t have to write this down)(pay attention but you don’t have to write this down)

Graphing GuideGraphing GuideSome rules to follow….Some rules to follow….

Graphs are an easy way to display your Graphs are an easy way to display your data.data.

Which graph you use depends on what Which graph you use depends on what data you have.data you have.

Bar Graph Pie Graph Line Graph

(Comparing trends & changes)

(Comparing parts of a whole)

(Comparing groups)

Graphing Guide Cont.Graphing Guide Cont. Always remember to title your graph.Always remember to title your graph. Independent Variable always goes on X-axis Independent Variable always goes on X-axis

(horizontal).(horizontal). Dependent Variable always goes on Y-axis Dependent Variable always goes on Y-axis

(vertical).(vertical). Label the X and Y axis.Label the X and Y axis. When graphing, use the “When graphing, use the “Dry-Dry-MixMix” to help you ” to help you

remember. remember. DDependent – ependent – RResponding –esponding –YY axis ----- axis ----- MManipulated – anipulated – IIndependent – ndependent – XX axis. axis. This will This will insure that all of your labels are correct!insure that all of your labels are correct!

PracticePractice(If we are taking the time out of class to work on practice

problems together it is in your best interest to follow along because you might see something similar on an upcoming assessment!)

James wants to perform an experimentJames wants to perform an experimenttesting how long it takes his dog Spot to eattesting how long it takes his dog Spot to eat3 different brands of dog food.3 different brands of dog food.

What is the independent variable?What is the independent variable?What is the dependent variable?What is the dependent variable?

Practice Cont.Practice Cont.

James records that Spot finishes James records that Spot finishes Brand C in the least amount of time, Brand C in the least amount of time, James then concludes that Spot must James then concludes that Spot must like Brand C dog food the best.like Brand C dog food the best.

What is the observation?What is the observation? What is the inference? What is the inference?