Transcript 2. Designing Experiments PPT

WELCOME
Please bring supplies as soon as you can
I suggest reviewing yesterday’s notes 
Intro:
How do you know that an experiment is good?
In other words, what are some characteristics
of good experiments?
DESIGNING AN EXPERIMENT
Most experiments involve two groups:
I. EXPERIMENTAL GROUP:
• Only one condition (variable) is changed
• Independent (manipulated) variable = the
condition changed by the experimenter
• Dependent (responding) variable = the
condition that changes because of the
independent variable
Hmm…
In the following experiment, identify the
independent and dependent variables.
Mrs. Pumpkin wants to know how much
fertilizer to use on her roses for best growth.
She divides her rose garden into three
sections. She fertilizes section A once per
year, section B twice per year and section C
three times per year.
Hmm…
In the following experiment, identify the
independent and dependent variables.
Mrs. Pumpkin wants to know how much
fertilizer to use on her roses for best growth.
She divides her rose garden into three
sections. She fertilizes section A once per
year, section B twice per year and section C
three times per year.
Independent Variable – number of fertilizations
Dependent Variable – growth of roses
DESIGNING AN EXPERIMENT
CONT.
II. CONTROL GROUP:
• All conditions are kept
constant
Hmm…
In the following experiment, identify the
control group, experimental group, and the
independent and dependent variables.
John is studying the effect of a new fever
reducing drug. He administers 50 mg of the
drug to 100 patients in Group I and 75 mg
to 100 patients in Group II. Group III does
not receive the drug.
Hmm…
In the following experiment, identify the
control group, experimental group, and the
independent and dependent variables.
John is studying the effect of a new fever
reducing drug. He administers 50 mg of the
drug to 100 patients in Group I and 75 mg
to 100 patients in Group II. Group III does
not receive the drug.
Control Group – III
Experimental Group – I, II
Independent Variable – mg of drug
Dependent Variable – reduction of fever
OTHER CHARACTERISTICS OF GOOD
EXPERIMENTS:
• Title (The effect of…on…)
• Testable hypothesis (If… then…, include #s)
• Constants (conditions that stay the same for all
experimental groups)
• Detailed, repeatable procedure
• Lots of repeated trials
Notes Summary
Write one paragraph the summarizes the main
points for this lesson. Your paragraph should
have an introductory and conclusion sentence.
You should write a minimum of 5 sentences.
Have a great semester!