Unit 2 Research Methods:

Thinking Critically with Psychological Science

I. The Need for Psychological Science

I. The Need for Psychological Science

A. Hindsight biasB. Overconfidence

98% Certainty

1. The area of the US in square miles?

2. The population of Australia 2007?

3. American battle deaths in Spanish-American War?

4. Female psychiatrists in the US in 2005?

5. Operating nuclear plants worldwide in 2007?

98% Certainty

1. Area of US:

2. Australian pop.:

3. Battle deaths:

4. Female psychiatrists:

5. Nuclear plants:

3.6 million sq. miles

20.4 million

385

13,079

435

I. The Need for Psychological Science

A. Hindsight biasB. OverconfidenceC. Scientific attitude 1. Curiosity 2. Skepticism 3. Humility 4. Critical thinking

II. How Do Psychologists Ask and

Answer Questions?

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles a. Theories b. Hypotheses c. Operational definitions d. Replication

Theory• Explanation using a set of principles that

organizes observations and predicts behavior or events– Not just a guess– Based on research and tested information– Organize isolated facts = simplify

Ex. “Sleep improves memory”

Hypothesis

• Testable prediction implied by a theory– Not an “educated guess”– A testable question based on a theory– Has testable predictions

Ex. “When sleep deprived, people remember less from the day before.”

Operational Definition• Statement of the exact procedures (operations) used

in a research study– Leaves nothing to subjectivity– Explains specifically

Ex. “Sleep deprived = X hours or less”

Let’s practice – create an operational definitionn for the following:

HappinessPopularityGood musicIntelligence

Replication

• Repeating the study, usually with different participants to see if the finding extend to others– To be a valid finding, it must be replicable

Scientific Method

Theory

Hypothesis

Research &Observation

Confirm, Reject,Revise

Don’t forget your operational

definitions so it can be repeated

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies

Phineas Gage1823-1860

(1) Problem?Can be misleading

(2) Why used?Provides study opportunities

not otherwise available

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys (1) Wording effects

72% interested in “plants & trees”39% interested in “botany”

1. Is the Mississippi River longer or shorter than 500 miles?

2. How many miles long is it?

1. Is the Mississippi River longer or shorter than 3000 miles?

2. How many miles long is it?

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys (1) Wording effects (2) Sampling (a) Populations

All those in group being studied (b) Random samples

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys c. Naturalistic observation

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques 3. Correlation and prediction a. Types b. Scatterplots

II. Asking & Answering Questions

Positive Correlation

Negative Correlation

No Correlation

II. Asking & Answering Questions

II. Asking & Answering Questions3. Correlation and prediction b. Scatterplots c. Correlation coefficients (useful at .2 and up/higher numbers

= greater predictability

II. Asking & Answering Questions3. Correlation & prediction c. Correlation coefficients d. Correlation does not establish cause & effect!!!!!!!

There is a correlation between TV watching and GPA

What do we know about cause and effect?

II. Asking & Answering Questions3. Correlation & prediction d. Correlation does not establish cause & effect!!!!!!! e. Illusory correlation

o perception of a relationship where none existso Ex: Getting wet and chilled causes people to

“catch a cold”o Ex: Infertile couples are more likely to conceive

after they adopto Sometimes we forget, random coincidences are

really are just random – we deceive ourselves by seeing a connection that isn’t there

II. Asking & Answering Questions3. Correlation & prediction d. Correlation does not establish cause & effect!!!!!!! e. Illusory correlation f. Random may not seem random

II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques 3. Correlation and prediction 4. Experimentation and causation

Experimentation

Purpose of an expt:

General hypothesis: food affects learning

Specific (operationalized) hypothesis: students who eat an oatmeal raisin cookie before class each day will have higher average scores on the semester final than students who don’t eat a cookie.

Eating cookies before class each day will lead to higher average scores.

Variables:Independent (IV)

Controlled by experimenterThe “cause” variable

Dependent (DV)Predicted by experimenterThe “effect” variable

Eating cookies before class each day will lead to higher average scores.

Groups (conditions): to establish different levels of the IV

Experimental groupExposed to IVGet cookie

Control groupNot exposed to IVNo cookie

What if kids get cookies and A’s?

Eating cookies before class each day will lead to higher average scores.

IV DV

Expt. Gp. Cookie 95%

Cntrl. Gp. No Cookie 82%

ConfoundingVariables

Environmental

Expectations

Individualdifferences

Random SamplingTo select participants from populationAllows you generalize results

Random AssignmentTo divide participants into groupsControls confounding variables

Eating cookies before class each day will lead to higher average scores.

IV DV

Expt. Gp. Cookie 95%

Cntrl. Gp. No Cookie 82%

85%

93%

Statistical Significance

p value

likelihood a result is caused by chance

can be no greater than 5%

p ≤ .05

Replication

Non-replicated results are preliminary.

Linus Pauling (1970). Vitamin C prevents colds.

IV DV

Expt. Gp. Vit C

Cntrl. Gp. Placebo

Expt. Gp.45%

Fewer colds

Experimental Design Terms

• Hypothesis• Operational definitions• Participant selection• IV & DV• Experimental & control groups• Confounding variables• Random assignment• Placebo control• Double blind procedure• Statistical significance (p value)• Replication

Quasi-experiments

• Men are better drivers than women.• Cigarette smoking causes lung cancer.

Practice with IV & DV

• Exposing children to public television improves their reading.

• You’ll have fewer problems in the future if you get psychotherapy.

• Getting complements makes people work harder on an assembly line.

Students are more likely to smile for their senior pictures if they have a friendly photographer.

IV?

DV?

III. Statistical Reasoning

III. Statistical Reasoning

A. Describing data

0. Frequency distributions

A 40 4 45%39 738 1037 836 15

B 35 8 32%34 833 832 7

C 31 4 16%30 529 728

D 27 5%26 225 124 2

F <24 1 1%

1. Bar graph (histogram) 2. Line graph (frequency polygon)

III. Statistical Reasoning

A. Describing data 0. Frequency distributions 1. Central tendency

43544

a. Mode --Most common=4 b. Mean --Arithmetic avg=20/5=4 c. Median --Middle score=4

Central Tendency 1968 TOPPS Baseball Cards

Nolan Ryan $1500

Billy Williams $8

Luis Aparicio $5

Harmon Killebrew $5

Orlando Cepeda $3.50

Maury Wills $3.50

Jim Bunning $3

Tony Conigliaro $3

Tony Oliva $3

Lou Pinella $3

Mickey Lolich $2.50

Elston Howard $2.25

Jim Bouton $2

Rocky Colavito $2

Boog Powell $2

Luis Tiant $2

Tim McCarver $1.75

Tug McGraw $1.75

Joe Torre $1.5

Rusty Staub$1.25

Curt Flood $1

With Ryan:Median=$2.50Mean=$74.14

Without Ryan:Median=$2.38Mean=$2.85

III. Statistical Reasoning

A. Describing data 0. Frequency distributions 1. Central tendency 2. Variation a. Range b. Standard deviation

Standard DeviationPunt

Distance

36384145

Mean=160/4=40 yds

Deviationfrom Mean

-4-2+1+5

DeviationSquared

16 4 125

46

46/4=11.5=variance

std. dev.=

variance=

11.5=3.4 yds

III. Statistical Reasoning

A. Describing data 0. Frequency distributions 1. Central tendency 2. Variation 3. The normal curve

III. Statistical Reasoning

A. Describing dataB. Making inferences 1. Can you generalize from sample to pop.? a. Is sample unbiased? Or is it a rep. sample? b. Is there low variability in sample? c. Is the sample large? More is better… 2. Is the diff. between two gps. stat. significant? a. Is the difference large? Is it reliable? b. Is there low variability within the groups? c. Is p ≤ .05?

IV. FAQs

VI. FAQs

A. Can lab expts illuminate real life?

B. How important are gender and culture?

C. Why study animals? Is it ethical?

D. Is it ethical to experiment on people?

E. How is psychology affected by values?

VI. FAQs

A. Can lab expts illuminate real life?– Focus is not on particular behavior, but on general

principles– Similar to using wind tunnel to build airplanes

VI. FAQs

B. How important are gender and culture?– Specific attitudes and behaviors can vary by

gender & culture, but underlying processes are often the same

– Kids everywhere like sports, but in the US you don’t usually find them playing barefoot in the street

– Men & women express/detect emotion differently, but both learn to walk about the same age

VI. FAQs

C. Why study animals? Is it ethical?– They have provided a cure for rabies,

understanding aging, relieving fears and depression

– Ethical… That is the debate and the answer varies by country and critter• Rats and sea slugs? Sure, but not puppies and

chimps…

VI. FAQs

D. Is it ethical to experiment on people? Yes, if the APA’s ethical guidelines are

followed.

1. Informed consent

2. Protection from harm

3. Confidentiality

4. Debriefing

VI. FAQs

E. How is psychology affected by values? – How and what we study• Worker productivity or worker morale?• Conformity or indepenence?

– How we describe things• Firm or stubborn?• Faith or fanaticism?

Assignments

• Must be word processed and printed out.• Must be ready by the beginning of the class

period.

How should participants be chosen?

• Good answers use and make clear your understanding of the terms “sample” and “population.”

• Good answers explain how to draw a random sample.

• Ex. “All the assembly line workers for a company could be the population. I would draw a random sample of 40 of them by picking names from a hat.”

Create operationalized hypothesis

• Good answers make an educated guess (“Workers who are complimented will work harder”)

• Good answers develop specific, measurable ways to define compliments and hard work.

• Ex. “10 compliments praising work effort will be given at four specific times.” “Supervisors will give compliments from a pre-developed list.” “Hard work will be measured by using the number of items produced each hour.”

Identify IV & DV

• IV=compliments• DV=work effort• Do not propose a direction when stating the

variable (“the DV is an increase in work.”)• People are never the variables (“the IV is the

people who get complimented.”)

Describe the groups

• Experimental group gets compliments.• Control group doesn’t get compliments.• Use the terms!

Confounding variables

• Do not confuse random assignment with random sampling.

• Issues related to complements are not confounding vars.

• Be reasonable!!!• “The company policy will be to have people

sleep in a hotel with no TV or radio.”• “I will provide a seminar on the importance of

sleep.”