Biostatistics For the Biological and Health Science

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BiostatisticsFor the Biological and Health
Science

• Chapter 3
• Probability

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Chapter Problem

• False positives and false negatives

Probability?
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3-1 Overview

• They reject explanations based on very low
  probabilities.
• Statisticians use the rare event rule.

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3-2 Fundamentals
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Relative Frequency
Classical
Subjective Probability
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Complementary events
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Ex P.98
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3.3 Addition Rules
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Probabilities play a very prominent role in
geneticslike Mendel
How many of them have green pods or purple
flowers? 8917?
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P(A ? B) P(A) P(B) P(A n B)
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Complementary Events
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3-4 Multiplication Rule Basics
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1/2 x 1/5 1/10
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Ex Plants P. 113 with replacement (????) vs.
without replacement (?????)
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3-5 Multiplication RuleBeyond the Basics

• Complements The Probability of At Least One

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Conditional Probability
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Confusion of the Inverse
P (BA) ? P (AB)
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Bayes Theorem (????)(determining probabilities
of events by incorporating information about
subsequent events)
(Subsequent events)
Ex P. 123
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Intuitive Bayes Theorem
P (MC) ?
4845/5678 0.85329341 0.853
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3-6 Risks(??) and Odds(?????)

• One way to measure risk is to use a probability
  value

Significant?
0.000164 0.000571
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EX P.131
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Odds (?????) or likelihood (???), such as 501
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Odd ratio
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Why Not Use Relative Risk for Retrospective
Studies?
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140/672 0.208
140/1204 0.116 ?
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3-7 Rates of Mortality, Fertility, and Morbidity
(optional)
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3-8 Counting
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Requirements
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Review Exercises

• ??Bayes Theorem , Risks and Odds ???,???????