Designing an Designing an ExperimentExperiment

The Scientific MethodThe Scientific MethodA problem solving technique based A problem solving technique based

on a logical progression of stepson a logical progression of steps

State the ProblemState the Problem

Gather infoGather info

Propose a hypothesisPropose a hypothesis

Test a hypothesisTest a hypothesis

Analyze dataAnalyze data

ConclusionConclusion

I have a great idea!I have a great idea!

As a scientist working for Exxon, I As a scientist working for Exxon, I want to prove Exxon gets better want to prove Exxon gets better

mileage than Lukoil!mileage than Lukoil!

Let’s design an experiment!Let’s design an experiment!

Gather info

Lukoil experimentLukoil experiment

Drive the Hummer Drive the Hummer upup Mt Mt PoconoPocono

Drive as fast as you canDrive as fast as you can

Fill a Hummer with Lukoil Fill a Hummer with Lukoil gas.gas.

Exxon experimentExxon experiment

Drive the SmartCar Drive the SmartCar DOWNDOWN Mt Pocono Mt Pocono

Drive as slow as you canDrive as slow as you can

Fill a SmartCar with Exxon Fill a SmartCar with Exxon gas.gas.

Analyze DataAnalyze Data

Lukoil = 1 mi/galLukoil = 1 mi/gal

Exxon = 100 mi/galExxon = 100 mi/gal

Let’s make some Let’s make some commercials and sell some commercials and sell some

Exxon!!!Exxon!!!

Fair Experiment?Fair Experiment?

biasbias Favoritism, or prejudice Favoritism, or prejudice towards a certain outcometowards a certain outcome

Where does bias come Where does bias come from?from?Past

experiencePersonal gainPeer pressure

Variables in an Variables in an experimentexperiment

Variable – factor which changesVariable – factor which changes

How many How many variables should a variables should a “fair” experiment “fair” experiment

have?have?

Variables in an Variables in an experimentexperiment

You need to change ONE thing at a You need to change ONE thing at a timetime

Then do the Then do the experiment and experiment and

see what see what happens.happens.

Variables in an Variables in an experimentexperiment

You need to change ONE thing at a You need to change ONE thing at a timetime

Then do the Then do the experiment and experiment and

see what see what happens.happens.

IndependeIndependentnt

VariableVariable

DependentDependentVariableVariable

Variables in an Variables in an experimentexperiment

Independent Independent VariableVariableThe factor in an The factor in an experiment you are experiment you are attempting to testattempting to testDependent Dependent VariableVariableThe factor you measure in The factor you measure in order to determine the effect order to determine the effect of the independent variableof the independent variable

Variables in an Variables in an experimentexperiment

Controlled Controlled VariablesVariablesThe factors in an The factors in an experiment you try to experiment you try to keep the same throughout keep the same throughout the experimentthe experiment

These are sometimes called These are sometimes called controls.controls.

Independent Independent variables answer the variables answer the question "What do I question "What do I

change?".change?". Dependent variables Dependent variables answer the question answer the question

"What do I "What do I observe?".observe?".

Controlled variables Controlled variables answer the question answer the question "What do I keep the "What do I keep the

same?"same?"