1. Scientific Method Steps
1. A. 6.
1. B. Observation 2. 5. 3. 4.

2. Experimental Research
An experiment is a scientific investigation that sets out to determine the cause and effect of two or more variables. A “good” experiment…
1. manipulates the independent variable
2. compares the groups in terms of the dependent variable
3. assures that only the IV causes the changes in the DV
if this is accomplished then the experiment has internal validity
4. minimizes confounding variables
any variable that varies along with the IV
5. uses randomization
6. uses experimenter control

3. Independent or Dependent?
Independent Variable
What the experimenter manipulates
The “cause” of the experiment
It is “independent” of all other variables
Dependent Variable
What the experimenter measures
The “effect” of the experiment
It “depends” on the Independent Variable

4. Independent Variable: Factors and Levels
 The Experimental Design depends on two things:
   The Number of Independent Variables (or Factors) used
One Factor is nice and simple
Two or more become Factorial Analysis
   The Number of Levels within each Independent Variable

5. Operational Definition
A definition of a variable that allows it to be concretely measured.
A variable is an Abstract Concept
It must be translated into a Concrete Form
so it can be measured
and studied empirically
Helps to successfully communicate ideas to others
Often a variety of measures are used

6. Dependent Variable Ceiling Effect Floor Effect
should be sensitive enough to detect differences between groups
Ceiling Effect
IV seems to have no effect only because participants quickly reach the
maximum performance level
Floor Effect
IV seems to have no effect only because the task is so difficult that
participants cannot perform well

7. Types of Data Categorical, Qualitative Variables: Nominal Ordinal
e.g., “yes/no”; “male/female”
Ordinal
e.g., “first, second, third”; “gold, silver, bronze”
Continuous, Quantitative Variables:
Interval
e.g., “temperature”
Ratio
e.g., “exam scores”; “GPA”

8. Independent or Between-Subjects
Requirements:
Each level of each independent variable has different subjects.
participants are randomly assigned to the different groups
random assignment prevents any systematic biases
Advantages:
minimizes order effects
minimizes demand characteristics
is the easiest to statistically analyze.
Drawbacks:
requires many subjects
less statistical power
takes more time
Control
Experimental
S01  S02  S03 
S04  S05  S06
S07  S08  S09 
S10  S11 S12

9. Order Effects Practice Effect Fatigue Effect Contrast Effect
order of presenting the treatments affects the dependent variable
Practice Effect
improvement in performance with repetition
Fatigue Effect
decrease in performance with repetition
Contrast Effect
second response is altered due to the influence of the first
Counterbalancing is used to correct order effects:

10. Counterbalancing Complete Counterbalancing Randomized Block Design
helps to minimize order effects
Complete Counterbalancing
Randomized Block Design
Matched Pairs Design
Latin Squares

11. Repeated Measures or Within-Subjects
Requirements:
Each subject participates in all levels of all independent variables
Advantages:
uses fewer subjects than the Between-Subjects Design
greater statistical power/ lower score variability
takes less time
minimizes subject effects 
Drawbacks:
is difficult to control order effects
increases demand characteristics 
Control
Experimental
S01  S02  S03  S04  S05  S06

12. Mixed-Subjects Requirements: Advantages: Drawbacks:
must be at least two independent variables
Each subject participates in all levels of just one independent variable
Advantages:
uses fewer subjects than the Between-Subjects
controls for order effects
controls for subject effects
Drawbacks:
is the most difficult to analyze statistically
Control
Experimental
S01  S02  S03  S04  S05  S06
S07  S08  S09  S10  S11 S12

13. Controls: Participants
Demand Characteristics
participants form expectations about the study and behave differently
typically "help" the scientists to support their hypothesis
deception helps to counter demand characteristics
filler items can be used on surveys to disguise the true DV
can ask the participants about their perspectives of the study
not really seen in non-participant field setting and naturalistic observations
Placebo Groups
typically used in drug studies
simulates drug taking protocol but has sugar pill replacement
placebo effect
just thinking you are taking medicine can improve your condition
can be a very powerful effect
Confederates and Deception
are used to keep the subjects from knowing the true nature of the experiment

14. Controls: Experimenter
All subjects need to be treated the same and the experiment must maintain consistency from start to finish.
Experimenter Bias
the experimenter inadvertently influences the outcome of the an experiment
may give one group of subjects hints on how to answer a question
could treat the control and experimental groups differently
can be biased in the way they score subjective evaluations
can make mistakes in data recording.
"teacher expectancy" can influence performance
just knowing about the study can influence the results
must assume the bias will happen if not corrected
Solutions to the Experimenter Bias
blind designs
single-blind experimental design
double-blind experimental design
simultaneous running of participants
experimenters should be well-trained and practice consistent behaviors
automatic/computerized scoring

15. Experimental Validity
Construct Validity
adequacy of the operational definition of variables
does it actually reflect the true meaning of the variable?
Internal Validity
ability to draw conclusions about causal relationships from our data
can you make strong inferences about one variable affecting another?
External Validity
the extent to which the results can be generalized to other populations and
other settings

16. Ethical Principles and Guidelines for the Protection of Human Subjects (Belmont Report)
Beneficience
maximize benefits and minimize risks
Physical harm
Loss of confidentiality
Justice
is there a fairness in giving benefits and accepting risks
Respect for Persons
allow subjects to make decisions as to whether to participate
Deception
Debriefing
Informed consent

17. Data Entry Should ALWAYS be done with TWO people Go very slow
Double Check your work
Save your spreadsheet often
Create an Excel Spreadsheet
Create an SPSS Spreadsheet
Save on Data Sticks and Bring to Class
Make Back-Up and leave at Home

18. Data Analysis
Graphs
Descriptive Statistics
Inferential Statistics