LUNCH N LEARN STATS

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LUNCH N LEARN STATS

• By Jay

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Course Goals

• Introduce / reinforce statistical thinking
• Understand statistical models
• Appreciate model assumptions
• Perform simple statistical tests

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Homework Review
GOAL learn more about the effects of ephedrine
on blood pressure. DATA charts of 20 patients
who received ephedrine during C-section in
1999.   QUESTIONS 1.     Define the population
referenced, and the cohort that is
sampled. 2.     Are these data observational or
experimental? 3.     Show a histogram of
?SBP. 4.     Suggest a better way to achieve your
initial goal.
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Homework Data
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HW 1, Question 1

• Define the population referenced
• Patients receiving ephedrine
• Define the cohort sampled
• Pregnant women who received ephedrine (criteria
  unknown) during C-section

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HW1, Question 2

• Are these data experimental or observational?
• OBSERVATIONAL

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HW1, Question 3 For critique
Histogram of DSPB
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HW1, Question 3
Histogram of DSPB
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HW1, Question 4

• Suggest a better was to achieve the initial goal
  learn more about the effects of ephedrine on
  blood pressure.
• Experimental, not observational
• Appropriate cohort
• Criteria for ephedrine administration

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New Concepts

1. A statistic is a function of the data.
2. Useful statistics have known distributions.
3. Statistical tests are based on a null
   hypothesis to be disproved.

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1 Statistic a function of data

• Average of all observations (mean)
• Average of the smallest and largest
• The middle observation (median)
• The largest observation
• The first observation

USES for estimation and testing
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Statistical Inference
mean, variance
95 Conf. Int.
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Concept 2 Useful Statistics

• Are unbiased (on average, hit the mark)
• Have minimal variance
• Have known distributions

Sample average Normal (m, s2/N) Sample average
t (m, s2/N) Sample standard deviation
s (N-1)s2/ s2 c2(n-1)
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Useful Statistics

• Suggest several useful statistics for the
  anti-hypertensive drug data and state the
  assumptions for each.

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Concept 3 Null Hypothesis
Statistical tests are based on a null
hypothesis to be disproved. EXAMPLES

• mT mP for DSBP
• MEDIANT lt MEDIANP
• s2T s2P

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Concept 3 Statistical Tests
Statistical tests utilize test statistics (duh?)

• To test equality of means mT mP and compare
  it to zero (0.0)
• To test equality of mediansSum of RanksT - ??m
  of RanksP
• To compare sample variances s2T / s2P and
  compare it to one (1.0)

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Session 2 Review

• New concepts
• Statistics are functions of the data
• Useful statistics have known distributions
• Statistical inference estimation testing
• Tests seek to disprove a null hypothesis
• Homework
• 20 patients given ephedrine during C-section