Medical Statistics Lecture Notes PDF

Medical statistics  Medical statistics : is the science of collecting, presenting, analyzing and interpreting data in medical practice, and using them to estimate the magnitude of associations and test hypotheses.  Functions of Statistics: 1. Presentation of da...

Medical statistics  Medical statistics : is the science of collecting, presenting, analyzing and interpreting data in medical practice, and using them to estimate the magnitude of associations and test hypotheses.  Functions of Statistics: 1. Presentation of data in a definite and simple form. 2. Comparison of health status: - of different localities, and in one locality at different times. 3. Diagnosis of a health problem in the community 4. Evaluation of any health program: e.g. vaccination programs.  DATA Definition: Set of values of one or more variables recorded in one or more observational units or numerical description of quantitative or qualitative aspects of things.  Types of data 1-Constant: Observation which does not varies from one person to another, E.g. number of chromosomes in a gene. 2- Variables: Observation which vary from one person to another.  Variables 1. Quantitative variables: Are expressed in numbers. They are either continuous or discontinuous. 2. Qualitative variables Also known as categorical variables, qualitative variables are variables with no natural sense of ordering. They are therefore measured on a nominal scale. For instance, hair color (Black, Brown, Gray, Red, and Yellow) is a qualitative variable, as is name (Mohamed, Ali, Adam, Mona, ….).  Discrete or Continuous discontinuous quantitative variable quantitative variable a. Always obtained by a. Always obtained by numeration. measurement b. The values take the b. The values may take form of the integer figures or integer figure (no fractions e.g.: weight, fractions): e.g. blood height, blood sugar, cells, number of urea, blood cholesterol, microbes /cc, respiratory Hb %. rate, number of beds in a hospital.  Ordinal / rank Nominal Variables whose Variables whose categories could be categories cannot be put arranged in a definite in any order e.g.: order: e.g 1. Sex: male or female 1-Educational level: 2.Marital status: single, a. illiterate, married, divorced, b. basic education, widowed. c. secondary, 3. Blood groups: A, d. university B,AB,O 2-Socioeconomic status: 4. Color of skin *high *middle *low. 5. Color of the eye 6. Religion. - Sometimes, quantitative variables could be transformed into qualitative one: Blood pressure could be expressed in numbers as: Quantitative qualitative ones 100/60................................hypotensio n  Data collection Data collection: is the process of gathering and measuring information on targeted variables in an established systematic fashion, which then enables one to answer relevant questions and evaluate outcomes.  Methods of data collection: 1. Historical records: e.g. a. Censuses b. Vital statistics records c. Epidemiological records d. Scientific journals and textbooks 2. Experimental. 3. Conducting surveys: a. Comprehensive surveys b. Sample surveys A-Comprehensive Surveys: The data are collected from every member in the community. This method is used for a small community e.g. a school, a village or a factory. B- Sample survey: The sample must be representative. In this method, the sample is collected from the population and the required data are collected from the sample members. Then, the results can be generalized over the whole population. - Characteristics of the sample: 1. The sample must be well chosen to be representative to the parent population. 2. The sample must be sufficiently large.