Transcript Statistics for Psychology

Lecture 02:
Chapter 1
Statistics for Psychology
David Wallace Croft
2005 May 18 Wed
Quiz 1
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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
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Absences
Calculators
Research Exposure Credits Requirement
Textbook Slides
Emphasis
Homework
Absences
• No makeup for daily quizzes
• Please limit missed exams to emergencies
• Early notification of absence is good
Calculators
• Not allowed for first exam
• Might be allowed for future exams
• Not sure yet
Research Exposure
Credits Requirement
• Detailed Handout
• Required to Complete Course
• Journal Article Option
– textbook footnote, p45
– Catanzaro, D., & Taylor, J.C. (1996). The
scaling of dispersion and correlation: A
comparison of least-squares and absolute
deviation statistics. British Journal of
Mathematical and Statistical Psychology, 49,
171-188.
Textbook Slides
• Chapter 1: Displaying the Order in a
Group of Numbers
– http://wps.prenhall.com/hss_aron_statistics_3/0,6590,401853-,00.html
Emphasis
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Boxes on Test
Frequency Polygon Zeroes
Direction of Skew
Median Household Income
Direction of Skew 1
“A skewed distribution has one side that is
long and spread out, somewhat like a tail.
The side with the fewer scores (the side
that looks more like a tail) is considered
the direction of the skew.”
-- textbook, p20
Direction of Skew 2
“In probability theory and statistics, skewness is a
measure of the asymmetry of the probability
distribution of a real-valued random variable.
Roughly speaking, a distribution has positive
skew (right-skewed) if the higher tail is longer
and negative skew (left-skewed) if the lower tail
is longer; getting these the wrong way round is a
common error.”
-- “Skewness”, Wikipedia
Median Household Income
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floor effect
skewed to the right
mean higher than median
mnemonic
Homework
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Optional
Do not turn in
Will help you on the exams
Answers to Set I problems in back of book
I have answers to Set II problems
Will help you on the exams
Next Class
• Friday
• Chapter 2
– Mean, Variance, Standard Dev, Z Scores
– Read Chapter 2 Before Class
• Pre-Lecture Quiz
– Starts at 09:00
– Ends at 09:02
• Exam 1 on Monday
Questions
• Questions for Class?
• Post to e-mail list unless personal
– http://egroups.com/group/utd-statistics