Lecture 4:Web Chapter 1

Statistics for PsychologyDavid Wallace Croft2005 May 25 Wed

Copyright 2005 David Wallace CroftThis work is licensed under the

Creative Commons Attribution License 2.0.

Quiz

• Please mute your mobile phones

• Write your name on a blank piece of paper

• Quiz will begin at 09:00

• When done, turn your paper over

• At 09:02, I will say, “Pens down”

• Writing after “Pens down” is cheating

• Pass your quizzes to your left

Outline

• See Saw Demo

• Scientific Method

• Web Chapter 1

• Exam Review

• Next Class

Hypothesis vs. Theory

• A Hypothesis is a theory

• A Theory is a thoroughly tested Hypothesis

– Atomic Theory– Cell Theory– Germ Theory

See Saw Demo

• Torque = moment of force

• Moment = product of distance from reference point and some other quantity

• Deviation= distance from mean= distance from balance point

Scientific Method

• Observe data

• Form hypothesis

• Test hypothesis with experiment

• Revise and retest

Scientific Method

• Observe nature• Form hypothesis• Test hypothesis using experiment• Revise hypothesis and retest

Scientific Method

• Observe data

• Form hypothesis

• Test hypothesis with experiment

• Revise and retest

Scientific Method 2

• Observe• Hypothesize• Predict• Verify• Evaluate• Publish• Reproduce

-- Wikipedia, ~2003-09-20

Web Chapter 1

Overview

of the

Logic and Language

of

Psychology Research

Web chapter for

Aron and Aron, “Statistics for Psychology”, 3rd Ed., 2003.

True Experiment

• Hypothesis: X causes Y

• Systematically vary X

• Everything else the same

Groups

• Experimental Group

• Control Group

• No control group

Participants

• Participants

• Subjects

Variables

• Independent variable

• Dependent variable

• Manipulate independent variable

• Dependent variable should follow

• If not, no cause-effect relationshipin that direction

Population vs. Sample

• Population

• Sample

• N – 1

Ideal Research Design

• Participants in both groups identical

• Identical situations except manipulated variable

• Sample represents population

• Measurement is accurate and appropriate

Participants Identical

• Random assignment

• No systematic difference

• Examples

Situations Identical

• Different room

• Different lighting

• Different time of day

• Different person giving instructions

• Avoid systematic difference other than manipulated variable

Double-Blind Experiment

• Placebo and Hawthorne Effect

• Experimenter bias

• Double-blind procedure

• Free weights

• Marital counselling

• Communication disorders

Representativeness of the Sample

• Sample vs. Population

• Generalizability or external validity

• Flukey sample

• Registered voters vs. likely voters

• College students

• Recruitment

• Random sampling

Measurement

• Accurate and Appropriate

• Inaccurate: grading or transcription error

• Inappropriate: bad question on exam

Significance of Statistics

• Back surgery• Cough suppressant• Hormone replacement therapy

-- Steven Bratman, “The Double-Blind Gaze: How the Double-Blind Experimental Protocol Changed Science”, Skeptic,

Volume 11, Number 3, 2005.

Exam Review

• Exam review next class

Next Class

• Friday

• Read Chapter 3 before class

• Quiz at start of class

• Monday no class

• Memorial Day

Questions

• Questions for Class?

• Post to e-mail list unless personal– ttp:// groups.com/group/utd statistics