Biostatistics

Annotations:

•   A field of study concerned with:  1- collection, organization, presentation summarization and analysis of data. 2- drawing of inferences about a body of data when only a part of the data is observed 

1. Descriptive statistics (Data summarization)

   Annotations:

   • Methods of organizing, summarizing, and presenting data in an informative way usually for one variable (Univariate)
   1. Graphical summarization

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      •  - We look for the overall pattern and for striking deviations from that pattern. - Over all pattern usually described by shape, center, and spread of the data.- An individual value that falls outside the overall pattern is called an outlier. 
      1. Bar charts and Pie charts are used for qualitative variables.
      2. Histogram, stem and leaf and Box-plot and others are used for quantitative variables
   2. Mathematical summarization
      1. Measures of Central Tendency

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         •   Measures which indicates where the middle of the data is. 
         1. Mean

            Annotations:

            •    Ithe average of the data.   The Population Mean is µ The Sample Mean is X bar
         2. Median
         3. Mode
         4. To be continued
      2. Measures of Dispersion
   3. Numerical summarization
      1. Numerical presentation of quantitative data
         1. Frequency Distributions
            1. Tabular
               1. Simple
               2. Complex
            2. Charts and graphs
               1. Histigram

                  Annotations:

                  •   Frequently used to graphically present interval and ratio data 
               2. Frequency Polygon

                  Annotations:

                  • -  Another common method for graphically presenting interval and ratio data    - If the purpose of presenting is comparison with other distributions, the frequency polygon provides a good summary of the data 
               3. Ogive

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                  •   A graph of a cumulative frequency distribution  
            3. Frequency distribution / count

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               •   presents the counts of observations grouped within pre-specified classes or groups 
            4. Relative Frequency Distribution / proportion

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               • presents the corresponding proportions of observations within the classes
            5. Cumulative Frequency Distribution

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               • the total of frequencies, that are distributed over different class intervals.
2. Inferential statistics

   Annotations:

   •   The methods used to determine something about a population on the basis of a sample two or more variables (multivariate) 
3. Data

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   •   - The raw material of Statistics is data, - Defined as figures ((Figures result from the process of counting or from taking a measurement)) or observation. 
   1. Types of data according to sources
      1. Primary data

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         •   collected specifically for the analysis desired. 
         1. Surveys

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            •   if the data needed is about answering certain questions. 
            1. Comprehensive
            2. Sample
         2. Experiments

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            • If the data needed to answer a question are available only as the result of an experiment. 
      2. Secondary data

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         • Data that have already been compiled and are available for statistical analysis. 
         1. Routinely kept records

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            • Like hospital medical records contain huge amounts of information on patients. 
         2. Literature or External sources

            Annotations:

            •   The data needed to answer a question may already exist as: published reports, commercially available data banks, or the research literature. 
   2. Constant
   3. Variable

      Annotations:

      •   It is a characteristic that takes different values in different persons, places, or things. 
      1. Qualitative variable

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         •   - are generally described by words or letters. - They are not as widely used as quantitative data because many numerical techniques do not apply to the qualitative data. 
         1. Nominal (names)

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            •   Gender, colour, name of villages 
         2. Ordinal / Rank

            Annotations:

            •   education levels Symptoms severity 
      2. Quantitative variables

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         •   are always numbers and are the result of counting or measuring attributes of a population. 
         1. Discrete (counting)

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            •   Children in family, Strokes on a golf hole 
         2. Continuous (measuring)

            Annotations:

            •   Amount of income tax paid, weight of a student
      3. Dependent / Response

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         •   The variable of primary interest (e.g. blood pressure in an antihypertensive drug trial). - Not controlled by the experimenter 
      4. Independent/Predictor (ID)
         1. Random variable
         2. Covariate

            Annotations:

            •   when not controlled. 
         3. Factor

            Annotations:

            •   - when controlled by experimenter. - It is often nominal (e.g. treatment)