Transcript BIOL 300: Biostatistics

BIOL 300: Biostatistics
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Statistical quotations
• There are three kinds of lies: lies, damn lies,
and statistics.
– Benjamin Disraeli / Mark Twain
Statistical quotations
• There are three kinds of lies: lies, damn lies,
and statistics.
– Benjamin Disraeli / Mark Twain
• It is easy to lie with statistics, but easier to
lie without them.
– Frederick Mosteller
Professor:
Dr. Luke Harmon
Department of Zoology
Office: 1370 Biosciences
Office Hours: 2 - 4 pm Mondays
(or after class)
e-mail: [email protected]
Course website
http://www.zoology.ubc.ca/~bio300/
• Lecture notes
• Textbook and Lab Manual
• Assignments and answers
• Contact information
Textbook
• Whitlock and Schluter, The analysis of
biological data
• Available in two installments at
CopieSmart, UBC Village
• Also available online
JMP
• Optional statistical
software
• Used in labs
• Available in
bookstore
• 60-day trial version
on web:
• www.jmp.com
Evaluation
Final
Mid-term
Assignments (homework)
Lab exam (final week of term)
50%
30%
10%
10%
Examinations
• Midterm: Thursday October 19 in class
• Final exam: TBA
• Old exams will be posted on the website
Assignments
• Available on course web-page, announced
in class
• Due on Fridays at noon, at your TA’s office
(eight days after they are assigned)
• Bonus points for in-class quizzes and
activities
Lab
• Begins third week of term
(September 18- 22)
• Biol. Sci. room 2434
• Lab exam during final week of classes
• Book available at Copiesmart in the village
and online
Class Forum
• There will be a forum for discussion on the
web
• Discussion of lectures, labs, and homework
• More details available next week
STATISTICS PAIRINGS
• Credit given for only one of BIOL 300,
FRST 231, STAT 200, PSYC 218 or 366.
• These are paired with BIOL 300, but do not
count as requirements for Biology majors
and pre-reqs
Introduction to statistics
Statistics - technology used to describe and
measure aspects of nature from samples
Statistics lets us quantify the uncertainty of
these measures
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http://www.rit.edu/~rhrsbi/GalapagosPages/DarwinFinch.html
The history of statistics has its
roots in biology
Sir Francis Galton
Inventor of fingerprints,
study of heredity of quantitative traits
Regression & correlation
Also: efficacy of prayer,
attractiveness as function of
distance from London
Karl Pearson
Polymath-
Studied genetics
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Correlation coefficient
c2 test
Standard deviation
Sir Ronald Fisher
The Genetical Theory of
Natural Selection
Founder of population genetics
Analysis of variance
likelihood
P-value
randomized experiments
multiple regression
etc., etc., etc.
Goals of statistics
• Estimation
– Infer an unknown quantity of a population
using sample data
• Hypothesis testing
– Differences among groups
– Relationships among variables
Statistics is also about good
scientific practice
Introductory Puzzle
• How to protect bombers flying over enemy
territory?
• British Air Ministry - WWII
• Looked at distribution of bullet holes in
airplanes returning from bombing runs
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http://digitalroam.typepad.com/digital_roam/2006/03/the_hole_story_.html
Results
• Where should more armor be added to the
airplanes?
• Explain your conclusion
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Variable
• A variable is a characteristic measured on
individuals drawn from a population under
study.
• Data are measurements of one or more
variables made on a collection of
individuals.
Explanatory and response variables
We try to predict or explain a response
variable from an explanatory variable.
Mortality on the Titanic, as
predicted by sex
Populations and samples
Populations <-> Parameters;
Samples <-> Estimates
Nomenclature
Population
Sample
Statistics
Mean
Parameters

Variance

s2
Standard
Deviation

s

x
Precise
Unbiased
Biased
Imprecise
Properties of a good sample
• Independent selection of individuals
• Random selection of individuals
• Sufficiently large
In a random sample, each
member of a population has
an equal and independent
chance of being selected.
Bias is a systematic
discrepancy between
estimates and the true
population characteristic.
A sample of convenience is a
collection of individuals that
happen to be available at the
time.
Sampling error
• The difference between the estimate and
average value of the estimate
Population parameters are
constants whereas estimates
are random variables,
changing from one random
sample to the next from the
same population.
Larger samples on average will
have smaller sampling error
Read: Chapters 1 & 2