Experimental design verision 3

Goal:
To be able to answer these two questions:
What is the experimental process?
(Inquiry or Scientific method)
What are the key considerations when designing an experiment?

1. Know the Big Picture - the Process of Science
Identify a
Problem

Identify a
Problem
Make
Observations
Make
Observations

a. Decide what to study
b. Identify key elements
(SS, MV, RV)
c. Create a scientific Question
1. Identify a Problem

Writing Questions
Study Subject =
Tulips
Manipulated Variable =
Fertilizer
Responding Variable =
Height
Question Format:
How will… MV and SS… affect…. the RV?
How will adding fertilizer to tulips affect the tulip’s height?
How will MV SS RV

2. Form the Hypothesis

2. Form a Hypothesis
Writing Predictions
If, Then - compared to Prediction format
If fertilizer is applied to tulips,
MV SS
Then the tulips with fertilizer will increase in height
Exp trial Definite prediction about RV
compared to tulips without fertilizer
Compare to Control

2. Form a Hypothesis
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
Because fertilizer has nutrients that increases tulip
growth. Thus the tulips with fertilizer will grow taller.
MV Specific reasoning SS
RV

3. Perform an Experiment
a. Materials
b. Trials
c. Variables
d. Procedure

a. Identify Materials

b. Set up Trials
Question 1: What are the two types, or groups, of Trials in an Experiment ?
Control and Experimental Trial
Question 2: What are the differences
between these two trials?
The Experimental Trial has the Manipulated Variable & tests the Hypothesis.
The Control does not have the MV and its results are compared to the Exp Trials

Example

c. The World of Variables

3. Perform an
Experiment

3. Perform an experiment
c. Controlling Variables
What are two ways to control
Variables?

Create a Controlled Environment

Expose all trials to the same changing conditions.

Which is ….?
Tulip Height
A Controlled
variable?
An Uncontrolled
Variable?
The Manipulated
variable?
The Responding
Variable?

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– Its only as good as the data gathered.
Week 1

Be consistent throughout the experiment.
Week Three

Ensure Reliability
Repeat the experiment 3x

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 error

9. Develop a Conclusion
a. State the question
b. Restate the Hypothesis
c. Tell if Hypothesis is Accepted or Rejected
i. Explain why using DATA (Hi, Low, Avg etc)
ii. Tell what you conclude from the data
iii. Make inferences from the findings
Clearly distinguish between the evidence
and your explanations.
iv. Evaluate the Reliability of the data
v. Tell sources of error & effect on results
vi. Describe how to increase the Validity.

Improving Validity
Experimenters do other trials to show that a change in the MV actually caused the change in the RV observed in their experiments.
Let’s explore a couple ways that might improve the
validity of the results from the Tulip experiment.
Assume that the class results show that the tulips with fertilizer added actually grew taller.

Validity Examples
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 Examples
b. Do more trials with another plant, like daffodils.
See if adding fertilizer increases daffodil height.
Daffodil Trials
Week 8

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

2a Create Prediction
Finalize details of
Experiment…..
Control & Exp Trials
2b. Form the Hypothesis
1b. Create Question
Develop question into
potential experiment.
Identify SS, MV & RV
3. Do the experiment
Gather data
Hypothesis
Rejected?
start over
4. Record & Analyze
the data
5. Draw Conclusions
Tell if Hypothesis
was accepted or rejected
discuss data and methods
6. Hypothesis
accepted
repeat 3x
Scientific Method… on paper!
1. State the Problem
Take data
Make Inferences
from data about
a problem.
7. Communicate results
to peers & defend.
Information becomes part of the world of science.

Do all first
Go back
Do Process
Do World of Variables
Do SS, MV, RV, QPH
Lead to Plungers as a group activity
UV Beads as a lab activity
Possibl
Add Reliability and Validity

Experimental design verision 3

by jschmied on Sep 22, 2010

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Experimental design verision 3 — Presentation Transcript