Experimental design verision 3

1. What is the experimental process? (Inquiry or Scientific method)

2. What are the key items to consider when designing an experiment?

Goal: to answer these questions:

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1. What is the experimental process?

Identify aProblem

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Identify aProblem

MakeObservations

MakeObservations

The basic steps

Create aTestablequestion

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1. Identify a Problem

c. Create a scientific Question

a. Decide what to study

b. Identify key elements (SS, MV, RV)

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Ex: Will tulips grow faster with fertilizer?

Study Subject =

Manipulated Variable =

Responding Variable =

How will adding fertilizer to tulips affect the tulip’s height?How will MV SS RV

How will… MV and SS… affect…. the RV?

Tulips

Fertilizer

Height

Question Format:

Writing Questions

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2. Form the Hypothesis

Hypothesis = Prediction with a reason

If, Then – compared to, Because format

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If fertilizer is applied to tulips,

Then the tulips with fertilizer will grow taller

If, Then - compared to Prediction format

compared to tulips without fertilizer

MV SS

Exp trial Definite prediction about RV

Compare to Control

Writing the Prediction

2. Form a Hypothesis

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Because fertilizer has nutrients that increases tulip growth. Therefore tulips with fertilizer will grow taller.

Hypothesis = Prediction with a reason

If, Then – compared to, Because format

Because includes SS, MV, RV & specific reasons why.

Prediction: If fertilizer is applied to tulips,

Then the tulips with fertilizer will increase in height

compared to tulips without fertilizer….

Adding a reason

MV Specific reasoning SS

RV

2. Form a Hypothesis

3. Perform an Experiment

a. Materials

d. Procedure

b. Trials

c. Variables

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3. Perform an Experimenta. Identify Materials

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Question 1: What are the two types, or groups, of Trials in an Experiment ?

Control and Experimental Trial!

Question 2: What are the key differences between these trials?

The Experimental Trial contains the Manipulated Variable & tests the Hypothesis.

The Control trial results are compared to the Experimental Trial results

3. Perform an Experiment -> b. Trials

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Example

3. Perform an Experiment

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c. The World of Variables

3. Perform an Experiment

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3. Perform an Experiment

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There’s only one MV

in anexperiment!

There can bemore than one RV in anexperiment

What are two ways to control

Variables?

c. Controlling Variables

3. Perform an experiment

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Create a Controlled Environment

3. Perform an Experiment

One way is to:

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Expose all trials to the same changing conditions.

3. Perform an Experiment

Another way to control variables is to:

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Identify …..

A Controlled variable?

The Manipulated variable? The Responding

Variable?

An UncontrolledVariable?

3. Perform an Experiment

Tulip Height

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d. Develop a Procedure

a. Create list of Materials

b. List procedural steps in order

Identify trials

Account for variables (only one MV!)

Includes: i. Jobs

ii. Safety Equipment (PPE) & hazards

iii. Clean Up

3. Perform an Experiment

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3. Perform an Experiment – Its only as good

as the data gathered.

Week 1

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3. Perform an Experiment Be consistent throughout the experiment.

Week Three

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3. Perform an ExperimentEnsure Reliability

Repeat the experiment 3x

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8. Analyze the Data

• Calculate Highs, Lows, Averages • Compare Experimental data to Control data• Look for Key Differences• Identify and Interpret patterns & variations• Make inferences from the data gathered

• Identify sources of errorschmied©2013

Error: What is error?

An error is a mistake in perception, measurement or process. The types of error are:

a. Experimental Design error:

b. Operator Error.

c. Observation Error:

d. Recording Error: 

e. Calculation Error: 

f. Measuring tool limitation.

a. State the question

b. Restate the Hypothesisc. Tell if Hypothesis is Accepted or Rejected

i. Explain why using DATA (Hi, Low, Avg etc)

9. Develop a Conclusion:

ii. Tell what you conclude from the dataiii. Make inferences from the findings

Clearly distinguish between the evidence and your explanations.

iv. Evaluate the Reliability of the datav. Tell sources of error & effect on results

vi. Describe how to increase the Validity.schmied©2013

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Elements of an experiment

To improve validity researchers do other trials to show that a change in the MV actually caused the change in the RV observed in their experiments.

Improving Validity

Let’s explore a couple ways that might improve the validity of the results from the Tulip experiment.

Assume that the original class results show the tulips with fertilizer added actually grew taller.

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A. Do more trials, each with different amount of fertilizer. Goal: See if a difference in tulip height can be linked to

the amount of fertilizer given.

Validity Example 1

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Daffodil TrialsWeek 8

b. Do more trials with another plant, like daffodils. See if adding fertilizer increases daffodil height.

Validity Example 2

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c. Do Tulip trials with varying concentrations of fertilizer, but add Daffodil trials too.

Validity Example 3

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7. Communicate results to peers & defend.Information becomes part of the world of science.

1. State the ProblemTake data

Make Inferencesfrom data about

a problem.

1b. Create QuestionDevelop question intopotential experiment.Identify SS, MV & RV

2a Create PredictionFinalize details ofExperiment….. Control & Exp Trials

2b. Form the Hypothesis

3. Do the experimentGather data

4. Record & Analyzethe data

6. Hypothesisaccepted repeat 3x

5. Draw ConclusionsTell if Hypothesiswas accepted or rejecteddiscuss data and methods

Hypothesis Rejected?start over

Scientific Method

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