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LUNCH N LEARN STATS

LUNCH N LEARN STATS. By Jay. Course Goals. Introduce / reinforce statistical thinking Understand statistical models Appreciate model assumptions Perform simple statistical tests. Homework Review. GOAL : learn more about the effects of ephedrine on blood pressure.

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LUNCH N LEARN STATS

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  1. LUNCH N LEARN STATS By Jay

  2. Course Goals • Introduce / reinforce statistical thinking • Understand statistical models • Appreciate model assumptions • Perform simple statistical tests

  3. 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.

  4. Homework Data

  5. 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

  6. HW#1, Question #2 • Are these data experimental or observational? • OBSERVATIONAL

  7. HW#1, Question #3: For critique Histogram of DSPB

  8. HW#1, Question #3 Histogram of DSPB

  9. HW#1, 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

  10. New Concepts • A statistic is a function of the data. • Useful statistics have known distributions. • Statistical tests are based on a “null” hypothesis to be disproved.

  11. #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

  12. ESTIMATION HYPOTHESIS TESTING Point Estimators Interval Estimators Statistical Inference mean, variance 95% Conf. Int.

  13. 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)

  14. TPL PPF 0 1 2 3 4 5 6 7 8 910 12 14 16 18 20 Useful Statistics Suggest several useful statistics for the anti-hypertensive drug data and state the assumptions for each.

  15. TPL PPF 0 1 2 3 4 5 6 7 8 910 12 14 16 18 20 Concept #3: Null Hypothesis Statistical tests are based on a “null” hypothesis to be disproved. EXAMPLES: • mT = mP for DSBP • MEDIANT < MEDIANP • s2T = s2P

  16. 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 medians:Sum of RanksT - 缀Ÿm of RanksP • To compare sample variances: s2T / s2P and compare it to one (1.0)

  17. 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

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