Thinking Critically with Psychological Science

Research & Statistics

Chapter 1

Critical Thinking

thinking that does not blindly accept arguments and conclusions

Examines discernsevaluates

AssumptionsHidden Valuesevidence

Limits of Intuition and Common Sense

Hindsight Bias

Overconfidence

But first…

A brief example of how NOT to conduct an experiment care of Dr. Venkman

Research Strategies

Theory

Hypothesis

The Scientific Method

generate or refine

research and observations

lead to

hypothesis

theories

Operational Definition

Example-IQ TESTS

Replication

Case Study

Survey

False Consensus Effect

Population

Random Sample

Research StrategiesIf marbles of two

colors are mixed well in the large jar, the fastest way to know their ratio is to blindly transfer a few into a smaller one and count them

Naturalistic Observation

observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation

Correlation Coefficient

a statistical measure of the extent to which two factors vary together and thus how well either factor predicts the other

Correlation coefficient

Indicates directionof relationship

(positive or negative)

Indicates strengthof relationship(0.00 to 1.00)

r = +.37

Scatterplot

–a graphed cluster of dots, each of which represents the values of two variables–the slope of the points suggests the direction of the relationship–the amount of scatter suggests the strength of the correlation–little scatter indicates high correlation–also called a scattergram or scatter diagram

scatterplots

Perfect positivecorrelation (+1.00)

No relationship (0.00) Perfect negativecorrelation (-1.00)

Scatterplot of Height and Temperament55 60 65 70 75 80 85

959085807570656055504540353025

Temperamentscores

Height in inches

Research StrategiesHeight and Temperament of 20 Men

12345678910

11121314151617181920

80636179746962757760

64767166737063716870

75666090604242608139

48697257637530578439

SubjectHeight in

Inches Temperament SubjectHeight in

Inches Temperament

Research Strategies

(1)Low self-esteem Depression

(2)Depression Low self-esteem

Low self-esteem

Depression

(3)Distressing events

or biologicalpredisposition

could cause

could cause

could cause

or

or

and

Illusory Correlation

Illusory Correlationthe perception of a relationship where none exists

Conceive Do not conceive

Adopt

Do notadopt

disconfirming evidence

confirming evidence

disconfirming evidence

confirming evidence

Random Sequences

Your chances of being dealt either of these hands is precisely the same: 1 in 2,598,960.

the investigator manipulates one or more factors (independent variables) to observe their effect on some behavior or mental process (the dependent variable) while controlling other relevant factors by random assignment of subjects

Experiment

Experiment cont.

by random assignment of participants the experiment controls other relevant factors

Double-blind Procedure

Placebo

Experimental Condition

Control Condition

Random Assignment

**minimizes pre-existing differences between those assigned to the different groups

Independent Variable **the variable whose effect is

being studied

Dependent Variable …in psychology it is usually a

behavior or mental process

Statistical Reasoning

Mode

Mean

Median

Statistical ReasoningA Skewed Distribution

15 20 25 30 35 40 45 50 90 475 71070

Mode Median Mean

One Family Income per family in thousands of dollars

Statistical ReasoningRange

Standard Deviation

Statistical Significance

Positive Skew

Negative Skew

polygon

HISTOGRAM