Experimental design verision 3
Post on 12-May-2015
2993 Views
Preview:
DESCRIPTION
Transcript
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:
schmied©2013
1. What is the experimental process?
Identify aProblem
schmied©2013
Identify aProblem
MakeObservations
MakeObservations
The basic steps
Create aTestablequestion
schmied©2013
1. Identify a Problem
c. Create a scientific Question
a. Decide what to study
b. Identify key elements (SS, MV, RV)
schmied©2013
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
schmied©2013
2. Form the Hypothesis
Hypothesis = Prediction with a reason
If, Then – compared to, Because format
schmied©2013
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
schmied©2013
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
schmied©2013
3. Perform an Experimenta. Identify Materials
schmied©2013
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
schmied©2013
Example
3. Perform an Experiment
schmied©2013
c. The World of Variables
3. Perform an Experiment
schmied©2013
3. Perform an Experiment
schmied©2013
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
schmied©2013
Create a Controlled Environment
3. Perform an Experiment
One way is to:
schmied©2013
Expose all trials to the same changing conditions.
3. Perform an Experiment
Another way to control variables is to:
schmied©2013
Identify …..
A Controlled variable?
The Manipulated variable? The Responding
Variable?
An UncontrolledVariable?
3. Perform an Experiment
Tulip Height
schmied©2013
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
schmied©2013
3. Perform an Experiment – Its only as good
as the data gathered.
Week 1
schmied©2013
3. Perform an Experiment Be consistent throughout the experiment.
Week Three
schmied©2013
3. Perform an ExperimentEnsure Reliability
Repeat the experiment 3x
schmied©2013
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
schmied©2013
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.
schmied©2013
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
schmied©2013
Daffodil TrialsWeek 8
b. Do more trials with another plant, like daffodils. See if adding fertilizer increases daffodil height.
Validity Example 2
schmied©2013
c. Do Tulip trials with varying concentrations of fertilizer, but add Daffodil trials too.
Validity Example 3
schmied©2013
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
schmied©2013
top related