Introduction to Statistics and Biostatistics and Definitions

1. WA 900 D184 1991WA 900 D184 1991 Daniel, Wayne W.Daniel, Wayne W. Biostatistics: A Foundation for Analysis in the Health SciencesBiostatistics: A Foundation for Analysis in the Health Sciences 2. WA 950 D272 2004WA 950 D272 2004 Dawson, Beth Trapp, Robert G.Dawson, Beth Trapp, Robert G. Basic & Clinical BiostatisticsBasic & Clinical Biostatistics Lange Medical Books/ McGrow-Hill NewYork 2004Lange Medical Books/ McGrow-Hill NewYork 2004 3. WA 950 G545 2002WA 950 G545 2002 Glantz, Stanton A.Glantz, Stanton A. Primer of BiostatisticsPrimer of Biostatistics McGrow-Hill NewYork 2002McGrow-Hill NewYork 2002 4. WA 950 A733 2002WA 950 A733 2002 Armitage, P.Armitage, P. Statistical Methods in Medical ResearchStatistical Methods in Medical Research Blackwell Science Oxford 2002Blackwell Science Oxford 2002

REFERENCE BOOKS

This course teaches the basic skills needed to critique the medical literature by providing a fundamental understanding of biostatistics.

Course Description

The primary purpose of this course is to teach you basic skills to critique the medical literature and need for statistical consultancy when designing, conducting and reporting a research. As future physicians you have an obligation to remain current in your field of practice and to treat patients according to generally accepted standards of care. To do this well you will need to read those journals that are considered the most important sources of new information impacting on your field of medicine.

For example, internal medicine physicians generally read the New England Journal of Medicine (NEJM) which is published by the Massachusetts Medical Society. Perhaps the most influential medical journal, its articles are widely reviewed by the media. Most surgeons read the Annals of Surgery. In short, each field of medicine has its own specialty journals.

As your patients hear media reports about the latest research results, they will most certainly ask for your opinion:

Should adult patients take antioxidants to Should adult patients take antioxidants to help prevent heart disease?help prevent heart disease?

Do the potential benefits of hormonal Do the potential benefits of hormonal replacement in postmenopausal women replacement in postmenopausal women outweigh the potential risks?outweigh the potential risks?

STATISTICS and BIOSTATISTICSStatistics is the art and science of data. It deals with •Planning Research

•Collecting Data

•Describing Data

•Summarizing- Presenting Data

•Analyzing Data

•Interpreting Results

• Reaching decisions or

discovering new knowledge

Biostatisitcs is the application of statistical methods to health sciences.

Basic tasks of statistics

•To describe

•To draw inferences concerning the underlying

population

ClassificationDescriptive statistics:These are devices for organizing data and may be: (i) tabular (ii) graphical (iii) numerical

Inferential statistics:Much of the statistical investigations are carried on samples. Conclusions about the population are thus drawn from the observations carried out on these samples. Statistical methods which are used for making inferences about the population are based on probability theory and are called inferential statistics.

Data : Set of values of one or more variables recorded on one or more observational units.

Observation (case): Individual source of data.

Variable: This is a quantity which varies such that it may take any one of a specified set of values. It may be measurable or non-measurable.

Population: A collection, or set, of individuals, objects, or measurements whose properties are to be analyzed.

Sample: A subset of the population, selected in such a way that it is representative of the larger population.

Parameter : A summary value which in some way characterizes the nature of the population in the variable under study.

Statistic : A summary value calculated from a sample of observation.

Data

Sources of data 1. Routinely kept records 2. Published data sources 3. Data on electronic media 4. Surveys and Experimental research5. Census 6. Generated or artificial data

Types of Data

1. Qualitative Data Results from a variable that asks for a quality

type of description of the subject.

2. Quantitative Data Results from obtaining quantities-counts or

measurements.

Qualitative (Categorical) Data

Nominal Ordinal Severity of disease Two

categories More than two

categories Income level

Marital Status Binary Dichotomous

Disease – or + Gender(M;F) BMI(<23;>=23)

Scale of measurement

Quantitative Data

Discrete Continuous # of birth # of death

Interval Ratio Temperature

IQ Age

Weight Height

Why should medical students learn biostatistics?

1. Medicine is becoming increasingly QUANTITATIVE.

• The aim is to improve the Health Status of the population.

• We have to clarify the relationships between certain factors and diseases.

• Enumarate the occurances of diseases

• Explain the etiology of diseases (which factors cause which diseases)

• Predict the number of disease occurence

• Read, understand and criticize the medical literature.

2. The planning, conduct and interpretation of much of medical research are becoming increasingly reliant on statistical methods.

Why should medical students learn biostatistics?

How many patients must be treated?

How do we have to allocate the subjects to treatments?

What are the other factors which may influence the response variable?

Planning:

Conduct:Under which conditions must the study be conducted?

Is matching necessary?

Is blinding (single blinding or double blinding) necessary?

Is there a need for a control group?

Shoud the placebo effect be considered?

Which experimental design technique is more appropriate?

Distribution of Women with a Diagnosis of Tromboembolism Among Blood Groups

Blood Group Frequency %

A 32 58.2

AB 4 7.3

B 8 14.5

O 11 20.0

Total 55 100.0

Distribution of Healthy Women Among Blood Groups

Blood Group Frequency %

A 75 51.7

AB 8 5.5

B 19 13.1

O 43 29.7

Total 145 100.0

Interpretation

Example 1

In a follow up study 609 males between ages of 40 to 76 free of coronary heart disease (CHD) were examined from 1990 to 1999. At the end of the period 71 new cases of CHD were identified. The primary goal of this study was to evaluate the association between obesity and the incidence of CHD. The results were as follows:

Disease

Obesity

TotalYes No

CHD+ 27 44 71

CHD- 95 443 538

Total 122 487 609

Risk Ratio= R

R=

The risk of CHD is 2.45 times higher among obese subjects.

487/44

122/27

Example 2