APPLIED Health Statistics 应用卫生统计 Professor Dr. Linn Carothers California Baptist University Summer, 2016

AGENDA 计划 What will we study.....

Today’s Agenda We will begin with an overview of the course and the syllabus Followed by a review and discussion of chapter 1 of the textbook 5

Chapter 1 Statistics and How They are Used

CHAPTER 1: Statistics and How They Are Used Professor Doctor Linn Carothers Natural and Mathematical Sciences 7

OUTLINE 1.1 The Meaning of Statistics Formally defines the term statistics and illustrates by describing what a statistic does 1.2 The uses of statistics Shows how descriptive statistics are used to describe data and how inferential statistics are used to reach conclusions from the analysis of data. 1.3 Why study statistics? Explains how the study of statistics is important for research, for writing publishable reports, for understanding scientific journals, and for discriminating between appropriate and inappropriate uses of statistics.

OUTLINE 1.4 Sources of Data Discusses surveys and experiments, two main sources of data, and further classifies surveys as retrospective or prospective and as descriptive or analytical. 1.5 Clinical Trials Describes the use of a clinical trial to determine the value of a new drug procedure. 1.6 Planning of Surveys Previews some hints on how to maximize the value of survey data. 1.7 How to Succeed in Statistics Offers some tips on getting the most out of class and other resources.

LEARNING OBJECTIVES 1. Define statistics 2. List several reasons for studying statistics 3. Distinguish clearly between Descriptive and inferential statistics Surveys and experiments Retrospective and prospective studies Descriptive and analytical surveys 4. Define bias 5. Describe the purpose and components of a clinical trial 10

THE MEANING OF STATISTICS What Does Statistics Mean? Often used to refers to a recorded data such as the number of students in a class, or the number of car crashes Also used to denote characteristics calculated for a set of data Means, standard deviation, correlation coefficient It is a body of techniques and procedures dealing with the collection, organization, analysis, Interpretation, and presentation of information that can be stated numerically 11

THE MEANING OF STATISTICS What Do Statisticians Do? Works on challenging scientific tasks Primarily concerned with developing and applying methods that can be used in collecting and analyzing data They have many tasks, which are as follows: To guide the design of an experiment or survey To analyze data To present and interpret results 12

INTERPRETATION OF STATISTICS An art and a science Even with results that are significant, it is important to scrutinize and examine the practical value Applicability and generalizability must also be addressed Are studies on heart disease applicable to women? What about studies on bone density and men? 13

THE USES OF STATISTICS There are two main types of statistics: 1. Descriptive Statistics – deals with the enumeration, organization, and graphical representation of data Example: Census 2. Inferential Statistics – concerned with reaching conclusions from incomplete information – generalizing from the specific Example: Opinion Poll (Gallup Poll) Statistical methods provide a logical basis for making decisions in a variety of areas when incomplete information is available 14

SMOKING DURING PREGNANCY Explored the effects of smoking on newborn infants in 1957 Examined data on 7,499 patients in 3 hospitals Found a correlation (relationship) between smoking and prematurity (early birth) Rates increased with the # of cigarettes smoked each day. “Maternal smoking during pregnancy has a significant adverse effect upon the well-being of the fetus and the health of the newborn baby.” 15

THE MULTIPLE RISK FACTOR INTERVENTION TRIAL (MRFIT) Exploring the effects of an intervention on coronary heart disease among middle-aged men 7-year trial with 20 clinical centers and 12,866 participants Random selection of half to the intervention and others to follow usual care Findings: Risk factor levels declined in both groups and any other difference were not found to be significant 16

THE FRAMINGHAM STUDY Began in 1948 to identify the factors that contribute to cardiovascular disease (CVD) Sample of 5,209 ages (disease free) across the community of Framingham, Massachusetts Currently in 2 nd and 3 rd generation cohorts Contributed to knowledge of major risk factors for CVD More than 800 scientific papers have been published 17

THE STAR TRIAL One of the largest breast cancer prevention studies Began in 1999 and ended in 2006, with more than 19,000 post menopausal women from more than 500 sites across US, Canada, and Puerto Rico Found that regular use of Tamoxifen or Raloxifene reduced risk of breast cancer in high risk women Also found an increase risk in uterine cancer and blood clots 18

WHY STUDY STATISTICS? Knowledge of stats is essential for both understanding and conducting research Learn how to answer the question, “does it work?” Used to analyze data Can help to discriminate between fact and fiction Helpful in knowing when, and for what purpose, a statistician should be consulted 19

SOURCES OF DATA When observing phenomena we gather information on characteristics, referred to as variables Data are the values for the variables Surveys and experiments are the two types of investigations With surveys, we obtain information but do not control or assign treatment/exposure With experiments, we design a research to intentionally impose controls over treatment/exposure 20

SOURCES OF DATA Retrospective Studies are those which rely on the collection of past data (aka case-control studies) Begins with knowledge of a specific disease or condition (cases) and also identifies a comparable sample without the condition (controls) Exposure is determined retrospectively Aim is to determine if the two groups differ on some factor Question: Is there a statistical relationship between exposure and outcome? 21

SOURCES OF DATA Retrospective Studies (aka case-control studies) Disadvantage – data usually collected for other purposes and may be incomplete There can be failure to include the relevant variables Hard to select appropriate controls Advantages Economical Answers usually obtained relatively quickly 22

SOURCES OF DATA Prospective Studies are those which allow for the following of healthy people over time (aka cohort studies) Begins with obtaining information on exposure and monitoring for outcome development Prospective determination of outcome Examples include the Framingham Study 23

SOURCES OF DATA Prospective Studies (cohort studies) Advantages C ollect relevant data to estimate incidence Collect data under uniform conditions and for specific reasons Better opportunities to draw appropriate conclusions or make appropriate comparisons while limiting or controlling the amount of bias Disadvantage – typically not used to establish or “prove” a causal relationship because variables cannot be randomly assigned or manipulated Very expensive and time intensive 24

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SOURCES OF DATA Descriptive Surveys – provide estimates of a populations characteristics Cross-sectional surveys Analytical Surveys – Seek to determine the degree of association between a variable and a factor in the population Retrospective, prospective, correlational 26

CLINICAL TRIALS Definition: A carefully designed experiment. It is considered to be the best method for evaluating the effectiveness of a new drug or treatment. 27

CLINICAL TRIALS Includes carefully planned protocol Describes in detail the design of proposed research Clearly defined hypothesis Detailed delineation of inclusion and exclusion criteria for study subjects Descriptions of the proposed interventions and the randomization process Detailed explanation of how bias may be minimized Description of the procedures to minimize errors in the collection and analysis of data 28

CLINICAL TRIALS Two key features Blinding – study subjects and/or the investigators do not know who is in the control group and who is in the experimental group with the purpose of reducing bias Single and double-blind study Randomization – subjects are randomly assigned to either the experimental or control group Doesn’t guarantee equivalent groups but does reduce bias by making groups as similar (equivalent) as possible 29

PLANNING SURVEYS Formulate a clear plan of action before starting a survey Outline major steps to be followed and what types of questions you want answered. Do you exercise? or How much exercise to you get each week? 30

HOW TO SUCCEED IN STATISTICS Scan the chapter outline Read the conclusion and vocabulary list Review the learning objectives before coming to class After class review terms and formulas Do the assigned exercises 31

CONCLUSION A statistician designs efficient and unbiased investigations that provide data that he or she then analyzes, interprets, and presents to others so that decisions can be made. To do this work the statistician uses techniques that are collectively called “statistics.” 32