1. INTRODUCTION TO BIOSTATISTICS

2. Role of a Doctor Clinician Manager Teacher Researcher

3. Medicine Medicine deals with individuals and groups who exhibit VARIATIONS in different characteristics such as –Weight –Blood pressure –Cholesterol level –Lung functions –HB levels etc

4. Variations The Healthy state of each characteristics Varies from person to person depending upon Biological factors No two persons or group of persons are ever exactly the same or alike

5. Variations Because of these variations, the outcome of decisions cannot be predicted exactly They are always accompanied by an element of uncertainty This is the Probabilistic nature of Medicine It is thus necessary to be conversant with the proper techniques for dealing with such variations and uncertainties

6. Medical Reasoning Deductive Reasoning Inductive Reasoning

7. Medical diagnostics, deductive reasoning can be divided into four basic processes: gathering facts, sorting facts, formulating differential diagnoses and arriving at solutions.

8. Dr. How’s Logic First patient: 1. Patient has been waiting for 30 minutes. 2. Patient has remained standing the entire time. 3. Therefore the patient is probably experiencing pain when he sits. 4. Patient has not explained why he is not sitting. 5. Patients who do not explain their problem right away are usually embarrassed by their problem.

9. 6. Therefore the patient is probably embarrassed by his problem. 7. Patient has a tattoo of a cartoon bird on his arm. 8. Therefore the patient is not easily embarrassed. 9. Hemorrhoids are not a particularly embarrassing medical problem. 10. Therefore the patient has a foreign object in his rectum.

10. In this Module Critical appraisal of literature How Biostatistics helps medical reasoning

11. Four Basic Process of Good Medical Diagnostics Gathering facts, sorting facts, formulating differential diagnoses and arriving at solutions.

12. Gathering the Facts “The world is full of obvious things which nobody by any chance ever observes”. THE HOUND OF THE BASKERVILLES, II:669-761*

13. Observation Key to gathering the facts Logical inference and theory are built on facts. We must know what we are looking for. This depends on investigation we undertake. There are only two ways to obtain data. –Verbal interview (taking the history). –Observation and scrutiny of objects (the physical examination). medicine usually depends heavily on the history.

14. Facts Should be gathered in depth Described and documented. Why? – because they may be transient. Observed fact may change when next observed. presence of certain facts may lead to certain conclusions, the absence of certain facts may be significant and lead to other conclusions. (eg. Cough and fever)

15. In this Module Learn how to collect and document facts Collection –Interview –Observation – measurements Documentation –Data types, rules for collection etc. –Data collection tools, data entry and analysis tools

16. Value judgments must be withheld until all the facts have been gathered and sorted, for faulty conclusions are drawn from insufficient data. Person comes with painless jaundice. Can it be cholelithiasis?

17. Sorting the Facts to eliminate facts unnecessary to the investigation and to list positive findings and pertinent negative findings. How does one go about sorting trivial from meaningful facts? The answer is experience in the field in which one is working.

18. the physician repeatedly tests them for reliability. He must conclude whether the items are trivial or relevant to the identification of the patient's disease. From the accumulated facts he must select for further consideration those symptoms and signs that his experience has taught are most likely to be helpful clues.

19. In this Module Data cleaning summarization Numerical – measures of central tendency, dispersion Graphical

20. Differential Diagnosis Having all positive findings listed, formulate explanations to fit the facts. From where do these explanations come? –store of accumulated and sorted facts –a physical file, a library of information or a reservoir of memories. We can train ourselves to observe and through experience we can learn to sort facts, but accumulating a file on which to base one's theories is a lifetime pursuit.

21. In this module Analysis and interpretation of collected data - Comparison within groups and population Apply statistical tests to support comparisons Review literature to support findings

22. Arriving at a Diagnosis We have a list of positive findings and a list of possible explanations. All we need do is fit the explanation to the findings. If we have a fact that contradicts one of our presumptive explanations, then our explanation is faulty and must be eliminated.

24. Statistical Concepts Probability Odds

25. Finding a Solution Based on Experience Based on scientific method

26. Scientific Method Observe some aspect of the Universe (Population) Invent Tentative description (Hypothesis) consistent with Observations Use Hypothesis to make predictions Test Predictions by experiments for further observations Repeat steps 3 and 4 until there are no discrepancies between theory and experiment and observation

27. Research - Definition Activities Designed to develop or contribute to generalizable knowledge –Theories, principles or relationships That can be corroborated by scientific methods of –observation, inference and/or experiment Advantage of scientific method –Unprejudiced, results repeatable, Theory Falsifiable

28. Definitions A theory is a conceptual framework explaining existing observations and predicts new ones Hypothesis is a working assumption

29. Descriptive Statistics Covers the organization and summarization of the data. It includes, Ways of ordering and grouping data into distributions Ways of calculating single numbers that summaries the whole data set Ways of representing data graphically

30. Inferential Statistics Inferences are drawn and decisions are made about a large body of data by examining only a small part of the data Helps to make educated guesses about a population, based on a random sample from a population

31. Why should I study Biostatistics? Health professionals are frequently faced with data on which they must base Clinical Judgment The reliability of support data plays a fundamental role in making good clinical decisions You must be able to distinguish between Discrepant data and Routine variability As a layman and as a Practitioner, you will be bombarded Daily with Statistics

32. Reasons for studying Biostatistics You must be able to read, understand and evaluate the medical literature in an intelligent manner You must be able to read the medical literature Critically

33. Reasons for studying Biostatistics You must understand terms such as “p-value”, “significance levels”, “confidence levels”, “standard deviation and errors”, “correlation”, “regression” etc Choice of statistical test and statistical interpretation.

34. No Need to memorize complex formulae Need to understand their application Use statistical packages and interpret results. Packages – Excel, Epiinfo

35. Statistical skills Helpful in developing a critical thinking faculty, in order to be able to Think scientifically, logically and critically about health problems Properly assess the available evidence for decision making Be aware of possible risks associated with medical decisions Identify decisions and conclusions that lack a scientific and logical basis

36. Assignment Explain with examples the two types of reasoning. What statistical principles are applied to the two types of reasoning. Define the terms variable, data, parameter, statistic, sample, population. Differentiate between descriptive and inferential statistics. Justify the need to learn statistics.

37. Thank You