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Key QuestionKey Question

What makes a good biology What makes a good biology experiment?experiment?

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Scientists ask questions Scientists ask questions about the world.about the world.

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Why ask the questions?Why ask the questions?

People are curious.People are curious.

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Farside Farside Cartoon: G. Cartoon: G. LarsonLarson

““Notice all the Notice all the computationscomputations, theoretical , theoretical scribblings, scribblings, and lab and lab equipment, equipment, Norm…Yes, Norm…Yes, curiosity curiosity killed these killed these cats.” cats.”

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What What Makes Makes A Good A Good Biology Biology Experi-Experi-ment?ment?

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What Makes a Good What Makes a Good Experiment ?Experiment ?

1. 1. 2.2. 3.3.

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What Makes a Good What Makes a Good ExperimentExperiment

1. Honesty1. Honesty 2.2. 3.3.

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What Makes a Good What Makes a Good ExperimentExperiment

1. Honesty1. Honesty 2. Scientific Method2. Scientific Method 3.3.

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What Makes a Good What Makes a Good ExperimentExperiment

1. Honesty1. Honesty 2. Scientific Method2. Scientific Method 3. Correct Equipment3. Correct Equipment

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WAIT! WAIT!

Scientific MethodScientific Method

……..What is that???..What is that???

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Start Note sheet Start Note sheet

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1. Ask a 1. Ask a testabletestable Question.Question.

Example: Example: Does watching Does watching T.V. make you fail T.V. make you fail Biology class?Biology class?

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2. Form a 2. Form a Hypothesis.Hypothesis.

Educated Educated guess.guess.Never in a Never in a questionquestion form.form.If/ThenIf/Then form formWhat is a good hypothesis for our What is a good hypothesis for our Bio grade/TV example?Bio grade/TV example?

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3. Design a 3. Design a Controlled Controlled Experiment:Experiment:

An experiment where only An experiment where only oneone variable variable is being changed at one time. is being changed at one time. There is a control group.There is a control group.And there is an experimental group .And there is an experimental group .

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3a. Control 3a. Control GroupGroup

The group that stays the same. The group that stays the same. The scientist keeps this group the The scientist keeps this group the same on purpose so we can same on purpose so we can compare compare the data with the the data with the experimental group.experimental group.Ex. plain cheeseburger vs. Big MacEx. plain cheeseburger vs. Big MacWhat is a good control group for the What is a good control group for the question biology grade and TV? question biology grade and TV?

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3b. 3b. ExperimentalExperimental GroupGroup

The group with the change. The group with the change. Only one variable (condition) is Only one variable (condition) is changed at a timechanged at a time..What is our experimental What is our experimental group? Bio grade/TV?group? Bio grade/TV?

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3c. 3c. Independent Independent VariableVariable

The variable the investigator is testing.The variable the investigator is testing.The variable the investigator is The variable the investigator is comparing.comparing.Ex. plain cheeseburger vs. Big MacEx. plain cheeseburger vs. Big Mac

IIndependent=ndependent=I I did itdid itOr Or

IIndependent = ndependent = IInvestigator did it.nvestigator did it.What is our independent variable?What is our independent variable?

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3d. Dependent 3d. Dependent VariableVariable

The variable that can be measured at end of The variable that can be measured at end of the experiment. the experiment.

What is our dependent variable? What is our dependent variable?

What can we measure after one group What can we measure after one group watches tons of TV and one group watches watches tons of TV and one group watches no TV? What can we compare?no TV? What can we compare?

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3e. 3e. ReplicationReplication::

Repeat the experiment many Repeat the experiment many times.times.

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The The numbernumber of subjects of subjects in the control & in the control & experimental groups.experimental groups.

3f. Sample Size:3f. Sample Size:

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3g. SAFETY!!!3g. SAFETY!!!For the researcherFor the researcher For the For the Environment Environment (Inside or outside labs)(Inside or outside labs) For the test subjects For the test subjects

(like animals)(like animals)

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Early Early Experi-Experi-ments ments in in TranspoTransportation.rtation.

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3h. Identify sources 3h. Identify sources experimental experimental errorerror..1. Bias: Preconceived ideas that 1. Bias: Preconceived ideas that influence influence experimenter.experimenter.2. Operator Error 2. Operator Error 3. Equipment Failure3. Equipment Failure

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3g. How can you prevent 3g. How can you prevent bias??bias??

Placebos- ½ test subjects give control or Placebos- ½ test subjects give control or fakefake variable variable

Blind Study-Blind Study- test subjects don’t know if test subjects don’t know if they have placebo or realthey have placebo or real

Double blind-Double blind- test subjects and test subjects and scientists don’t know who has placebo or scientists don’t know who has placebo or realreal

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4. Collect Data.4. Collect Data.Think about how best Think about how best to set up a to set up a data data sheet.sheet.

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5. Analyze 5. Analyze data.data.

Create a Create a graph,graph, chart, or chart, or map to organize collected map to organize collected data. data.

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6. Form 6. Form conclusions.conclusions.

What What patternspatterns do you do you see? see?

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7. Repeat 7. Repeat Experiment.Experiment.

Do not Do not change change any any variables!variables!

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Wrap UpWrap Up

What makes a good biology What makes a good biology experiment?experiment? HonestyHonesty Scientific methodScientific method Correct equipmentCorrect equipment